The Physics of a Rolling Rubber Band

Physics... by Pojut · 2010-07-29 00:48 · Score: 3, Insightful

...is mind-boggingly awesome. I can't understand the math at all, but I understand the way things generally act. So cool (and so insanely complicated! Think about something like a key being inserted into a lock...and that's just simple, everyday stuff!)

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Living With a Nerd

Re:Physics... by SpinningCone · 2010-07-29 01:01 · Score: 4, Interesting

i agree. I always liked physics made the world look different (like "car breaks are kinetic to thermal energy converters"). never could really get into dynamics though. i remember my teacher describing the the problem of rotational inertia of a deformable object (like a jelly disk) faster you spin the more it changes shape which changes its inertia.
props to the people out there with the knack and persistence to solve crap like that.
Re:Physics... by Anonymusing · 2010-07-29 01:02 · Score: 4, Funny

Physics is pretty cool.
I liked this quote from the article:

As far as the potential applications, Clanet waxes futuristic. "I can imagine [designing] a car. The faster it goes, the more it deforms and the less friction it has with surrounding air, so it can go even faster. It would be a fantastic car."
A car that changes its shape as it drives? Getting shorter, even? "Ouch, slow down, you hit my head!"
Automobile safety experts would have a field day with that.

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Re:Physics... by snookerhog · 2010-07-29 01:10 · Score: 1

the vehicles changing shape comment reminds me of the SR71. Only when it gets up to speed do the joints close up and the skin smooth out due to air friction heating it up. The think leaked fuel like a sieve on the tarmac apparently, but was tight as a frog's ass at mach 3.
Re:Physics... by zaaj · 2010-07-29 01:13 · Score: 1

Yeah, that quote bothered me too - I'm thinking, why not just design it with the least friction with the air to start with - why have it be less efficient at slow speeds in other words?
Unless Clanet was referring to the design process itself - use an elastic model in a wind tunnel (or simulate the whole thing) and observe it's deformation to determine the shape with the least friction with the air (or call it coefficient of drag, like everyone else does :-)
At first I was thinking it might have been typical media-distorted science, but when they threw in that quote from Clanet, it seemed more that the science is hard to take seriously too.
Re:Physics... by Seismologist · 2010-07-29 01:19 · Score: 2, Interesting

...is mind-boggingly awesome.
Actually you can often make a simple assumption and work off of F = m*a or some other well established theorem...
As for the math, now that is some pretty mind boggling stuff. Some of the math that was used to pull string theory together is pretty bleeding edge on top of the physics part of it. PBS had a interesting show on string theory(you can watch in three installments on PBS). What struck me the most was how splintered the physics community was as many researches were doing the math a certain way different from each other, but it was found to be all the same by another physics/math guru when he proposed 11 dimensions instead of 9 like the other researches had inferred.

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~ In Trust, We Trust ~
Re:Physics... by GNUALMAFUERTE · 2010-07-29 01:26 · Score: 0, Troll

Oh, if you don't understand the math at all, then you are totally qualified to write articles for sciencemag.org.
Here is how it basically works:
1) You made some dull experiment, very simple setup, that leads nowhere, and allows no data collection at all.
2) Write down "Woah, awesome, if were like it would be, like, great, amirite?
3) Publish.
4) ???
5) Get to the frontpage of /.
The article reminded me of this: http://xkcd.com/171/

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Re:Physics... by EdZ · 2010-07-29 01:31 · Score: 3, Insightful

Because air behaves differently at different speeds. Once you got fast enough, shockwaves become the limiting factor rather than fluid fraction. Then you have cavitation, and things like compression heating. What is most efficient at one speed is not most efficient at all speeds.
Re:Physics... by Anonymous Coward · 2010-07-29 01:37 · Score: 0

best xkcd ever!
Re:Physics... by VolciMaster · 2010-07-29 01:47 · Score: 3, Funny

I love Ben Rich's quote on that: "no one's been wing-walking at Mach 3 to verify that assumption" :)

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antipaucity
Re:Physics... by VolciMaster · 2010-07-29 01:52 · Score: 2, Insightful

Yeah, that quote bothered me too - I'm thinking, why not just design it with the least friction with the air to start with - why have it be less efficient at slow speeds in other words?
Unless Clanet was referring to the design process itself - use an elastic model in a wind tunnel (or simulate the whole thing) and observe it's deformation to determine the shape with the least friction with the air (or call it coefficient of drag, like everyone else does :-)
At first I was thinking it might have been typical media-distorted science, but when they threw in that quote from Clanet, it seemed more that the science is hard to take seriously too.
Just a quick thought, but at low speeds aerodynamic efficiency is of very low impact (eg a barge at 2 kts and a kayak at 2 kts). The faster they go, the more that efficiency matters - having a material that could deform to improve flow as speeds increased could be a good thing - especially if it were used around the freight compartments of a tractor-trailer or rail car: squishing-down to more evenly flow around the carried contents could have some promise.

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antipaucity
Re:Physics... by Anonymous Coward · 2010-07-29 02:07 · Score: 0

Fucking keys, how do they work?
Re:Physics... by Anonymous Coward · 2010-07-29 02:31 · Score: 0

so you're saying if i roll a peanut down an incline that it'll make peanut butter if it goes fast enough?
is this peanut butter going to be spread down the incline or is it going to be at the very end, where the incline hits a giant BRICK WALL? :)
Re:Physics... by AndersOSU · 2010-07-29 02:56 · Score: 1

It gets even more interesting than that. There's two main types of drag, friction drag and pressure drag. Friction drag is generated from air molecules slamming into the object and the fact that very close to the surface of the object the fluid is slowed (known as the no-slip condition). Pressure drag is a bit less intuitive, but it's what makes drafting work in both nascar and cycling. As you speed up an area of low pressure develops behind you as the flow separates at the back of the object. This low pressure literally sucks you backwards. Finally there is a discontinuity in drag at mach 1 when shock waves and the like develop.
At low speeds friction drag tends to dominate and this drag can be reduced by improving the aerodynamics of the leading edge of the object. At high speeds pressure drag tends to dominate and this can be reduced by modifying the trailing end of the object - which why time-trial racing bike helmets are pointed at the back. The other thing you can do is add texture which separates the flow from the object and usually reduces the size of the low pressure bubble behind it, and this is why golf balls are stippled.
One last interesting bit. The angle the shockwave of a supersonic object takes is a function of speed, not shape. If you're a plane designer you want the largest wing area as possible within that shock wave (things projecting into the shock have a nasty tenancy to be ripped off.) So while the top speed of the SR-71 is still technically classified (or at least it was when I took fluid dynamics), by measuring the angle from the nose to the wingtips you can calculate the top design speed remarkably easily.
Re:Physics... by Twinbee · 2010-07-29 03:15 · Score: 1

That sounds interesting. Can you give the associated speeds that those things separate phenomena start to occur at?

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Why OpalCalc is the best Windows calc
Re:Physics... by Anonymous Coward · 2010-07-29 03:24 · Score: 0

those problems you are talking about are called "differential equations", and guess what, you couldnt get into them because they are in fact, fucking heavy shit, and most often not even analytically solvable. that jelly disk though, is. assuming linear deformation. id recommend you to start reading into the harmonic oscillator if you want to dig into diff equations.
Re:Physics... by Anonymous Coward · 2010-07-29 03:59 · Score: 0

And don't even get me started about magnets...
Re:Physics... by Chris+Burke · 2010-07-29 04:16 · Score: 1

Just a quick thought, but at low speeds aerodynamic efficiency is of very low impact (eg a barge at 2 kts and a kayak at 2 kts). The faster they go, the more that efficiency matters - having a material that could deform to improve flow as speeds increased could be a good thing - especially if it were used around the freight compartments of a tractor-trailer or rail car: squishing-down to more evenly flow around the carried contents could have some promise.
The question, though, is why does not having an efficient shape at low speeds matter, if you have to be able to assume an efficient shape anyway? If you have a vehicle designed to be able to travel at speeds where it matters, why not design it with an aerodynamic shape to begin with?
Since it won't let you carry more cargo, the only thing that comes to mind is maybe ease of loading and unloading cargo. Which it seems like there are easier ways to address.
Besides, land and water based freight is more about throughput not velocity. We aren't going to replace a huge freighter with it's giant pile of stackable shipping containers with some speedy aerodynamic thing. When we want shipping to be fast, we use planes, which are already designed to be aerodynamic. :)

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The enemies of Democracy are
Re:Physics... by Chris+Burke · 2010-07-29 04:24 · Score: 1

You can tell from photos at low velocity/altitude (and many reports from people who worked on them) that they leaked... But it's true, nobody has verified that they stop.

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The enemies of Democracy are
Re:Physics... by Anonymous Coward · 2010-07-29 04:34 · Score: 0

How am I trolling? There was actually no fucking science at all in that article. That's a fucking shame.
Re:Physics... by ehrichweiss · 2010-07-29 04:39 · Score: 1

I didn't see this in TFA but I suspect they might find something a bit different about this behavior if they performed the rolling in a vacuum. I say this because some 15+ years ago I observed the deformation that they're talking about due to a magic trick I perform where I "shoot" a rubber band forward really fast and then it rolls back toward me like it was a boomerang, and it has little-to-nothing to do with aerodynamics; it has far more to do with the physical qualities of the "rubber" and the inertia of the material in the rear as it moves from touching the ground to being "lifted" to be brought back to the front. You see this behavior in many things including some chainsaws if their chains are really loose.

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0x09F911029D74E35BD84156C5635688C0
Re:Physics... by Menkhaf · 2010-07-29 07:23 · Score: 1

Found the Wikipedia article on the Lockheed SR-71 Blackbird after reading your comment (last paragraph in "Titanium structures and airframe"):
"To allow for thermal expansion at the high operational temperatures, the fuselage panels were manufactured to fit only loosely on the ground. Proper alignment was only achieved when the airframe heated due to air resistance at high speeds, causing the airframe to expand several inches. Because of this, and the lack of a fuel sealing system that could handle the thermal expansion of the airframe at extreme temperatures, the aircraft would leak JP-7 jet fuel onto the runway before it took off. The aircraft would quickly make a short sprint, meant to warm up the airframe, and was then refueled in the air before departing on its mission. Cooling was carried out by cycling fuel behind the titanium surfaces at the front of the wings (chines). On landing after a mission the canopy temperature was over 300 C (572 F), too hot to approach. Non-fibrous asbestos with high heat tolerance was used in high-temperature areas.[20]"

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Re:Physics... by Anonymous Coward · 2010-07-29 07:59 · Score: 0

Physics is pretty cool.
I liked this quote from the article:

As far as the potential applications, Clanet waxes futuristic. "I can imagine [designing] a car. The faster it goes, the more it deforms and the less friction it has with surrounding air, so it can go even faster. It would be a fantastic car."
A car that changes its shape as it drives? Getting shorter, even? "Ouch, slow down, you hit my head!"
Automobile safety experts would have a field day with that.
This actually exists, Ferrari's new vehicle has winglets in the front fascia that deform at speed to change the way the air flows to create more downforce and make the car faster.
Re:Physics... by JWSmythe · 2010-07-29 10:05 · Score: 1

I saw a video of a prototype of that once several years ago. It was the BMW "Gina". The whole skin of the car was a stretchable fabric, which did away with most of the body panel seams. Neat idea. Too expensive to produce.
It's silly to think that a car that changes shape is a good idea. It's easier for them to produce an aerodynamic car which performs well at the intended max speed, yet leaves enough room inside for the passengers. Why would you want to build a car with a suboptimal aerodynamic profile, for it to just change to the optimal profile when driving at high speed? It's not like they're building cars that need to transit the sound barrier or something, and the body does not provide lift (hopefully). Something like an F-14 needed to be able to change its configuration for low and high air speeds, but obviously that isn't necessary since most supersonic aircraft don't do it.

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Re:Physics... by Anonymous Coward · 2010-07-29 10:34 · Score: 0

And that's why we already have some luxury sports cars with rear spoilers that extend/retract depending on the speed.
Re:Physics... by Anonymous Coward · 2010-07-29 11:44 · Score: 1, Informative

But all cars get shorter as they get faster - it's the Lorentz-Fitzgerald Contraction (http://en.wikipedia.org/wiki/Length_contraction), due to approaching the speed of light.
Re:Physics... by Thing+1 · 2010-07-29 13:13 · Score: 2, Interesting

The other thing you can do is add texture which separates the flow from the object and usually reduces the size of the low pressure bubble behind it, and this is why golf balls are stippled.

I remember a MythBusters episode where they added a bunch of clay to a car (adding quite a bit of body weight), and then carved out dimples like a golf ball would have.
The car ended up getting better fuel efficiency than the original (lighter, smoother) car. I was really impressed, especially because it had to overcome the added weight.

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Re:Physics... by VolciMaster · 2010-07-30 00:47 · Score: 1

Oh yeah: on the ground it rained.. and theoretically quit at speed - but it would've been fun to have some kind of proof they did :)

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antipaucity
Re:Physics... by sayno2quat · 2010-07-30 01:22 · Score: 1

Actually, they specifically took the weight out of the equation. They didn't start calculating the loss of fuel until after getting up to a certain speed. So I highly doubt it got better gas mileage from 0-60, since the added mass definitely took a toll. But keeping a vehicle at constant speed negates (for the most part) any weight, allowing them to measure the fuel efficiency based mainly on the shape of the car.

For those who didn't see the episode, here is what they did (in a little more detail).
They set up a long track with a start and end point. They accelerated a car way before the start point, and kept it at a constant speed from the start point to the end point, only calculating fuel efficiency from that point.
After that, they added a whole bunch of clay to the car. They shaped it to the car's mold, then did another test.
Then, they cut dimples out, making it look like a golf ball. They put the cut-out clay in a box in the car, so that it weighed the same. Then they tested the gas mileage. The car with the dimples got better gas milage than both the smooth-clay car and the car before any clay.

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Sure I sold you robot insurance. But you were attacked by a cyborg. Not covered.

Delight to read... by ZeroExistenZ · 2010-07-29 00:51 · Score: 2, Funny

But what happens when a deformable shape like a rubber band rolls around?

... the article sounds like the things I used to wonder about and do during boring classes in highschool.

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Re:Delight to read... by jamesh · 2010-07-29 00:58 · Score: 2, Funny

... the article sounds like the things I used to wonder about and do during boring classes in highschool.
Same here, except I was more like "I wonder if I can hit that kids sticking-out ears with a rubber band from here", without thinking through what would happen if i _did_ hit them (which should have been obvious in retrospect... it was for that reason I sat at the back).
Re:Delight to read... by Spad · 2010-07-29 01:14 · Score: 4, Funny

I like to imagine that all scientists operate on this principle. They sit around doing boring paperwork until one of them says "I wonder what happens when a deformable shape like a rubber band rolls around?", to which one of the others replies "Quickly, to the lab!" and they all run off to investigate it.
Re:Delight to read... by gl4ss · 2010-07-29 01:24 · Score: 1

if it's worth publishing, I'd have hoped for it to be worth to them to have an incline to roll it down on, instead of having it in a rolling drum. like, get out of the damn room if it's too small. now i'm just left wondering if it spun along with the drum and got squashed because of that.

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Re:Delight to read... by VolciMaster · 2010-07-29 01:53 · Score: 1

... the article sounds like the things I used to wonder about and do during boring classes in highschool.
Same here, except I was more like "I wonder if I can hit that kids sticking-out ears with a rubber band from here", without thinking through what would happen if i _did_ hit them (which should have been obvious in retrospect... it was for that reason I sat at the back).
..guess it depends on how big the kid with the sticking-out ears was, eh?

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antipaucity
Re:Delight to read... by VolciMaster · 2010-07-29 01:54 · Score: 1

if it's worth publishing, I'd have hoped for it to be worth to them to have an incline to roll it down on, instead of having it in a rolling drum. like, get out of the damn room if it's too small. now i'm just left wondering if it spun along with the drum and got squashed because of that.
maybe they used a drum because setting-up a camera along a 50 foot ramp would've been cost-, space-, or effort-prohibitive?

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antipaucity
Re:Delight to read... by Scatterplot · 2010-07-29 02:11 · Score: 2, Funny

No, it depends on how fast he was rolling. I think.
Re:Delight to read... by PitaBred · 2010-07-29 03:30 · Score: 1

If you want to make sure you do hit the ear, make one "side" of the rubber band tighter than the other when you shoot it. It makes it spin in flight and stabilizes it's trajectory. I can nail a fly from 10' with the right technique ;)

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Re:Delight to read... by painandgreed · 2010-07-29 04:34 · Score: 1

I like to imagine that all scientists operate on this principle. They sit around doing boring paperwork until one of them says "I wonder what happens when a deformable shape like a rubber band rolls around?", to which one of the others replies "Quickly, to the lab!" and they all run off to investigate it.
Actually, that's a pretty good description of lunch with physicists. Except, first we'd have to write down the physical constants of the rubber band, derive the dynamic equations of motion for the rubber band, find the expected behavior, and then run off to the lab to see if our results were correct with the last half of our lunchtime.
Re:Delight to read... by gstoddart · 2010-07-29 05:16 · Score: 1

Actually, that's a pretty good description of lunch with physicists. Except, first we'd have to write down the physical constants of the rubber band, derive the dynamic equations of motion for the rubber band, find the expected behavior, and then run off to the lab to see if our results were correct with the last half of our lunchtime.
So, what, physicists only do physics during lunch?
The rest is all paperwork? How lame. :-P

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Re:Delight to read... by painandgreed · 2010-07-29 05:36 · Score: 1

So, what, physicists only do physics during lunch?
No, first we each lunch. Then we get distracted. Everything else is paperwork. First you have the theoretical physics which is paperwork, then after you do the experiments and have to write down all your data and findings, then write up the paper, which is more paperwork.
Re:Delight to read... by Anonymous Coward · 2010-07-29 07:17 · Score: 0

"Elastic bands roll for a maximum of 50 feet then suddenly disappear" is still being confirmed. They figured that the drum would allow them to focus on the band for longer periods of time.
Re:Delight to read... by jamesh · 2010-07-29 12:59 · Score: 1

..guess it depends on how big the kid with the sticking-out ears was, eh?
Not really. Size wasn't that important. Kids half my size could pretty easily beat me up.

Wow, interesting! by rotide · 2010-07-29 00:58 · Score: 4, Interesting

If you would have asked me how it would react as it rolled faster and faster, I would have just assumed it would have gotten "rounder" and possibly larger (elastic) due to centrifugal force.

Always amazes me how things don't always work as expected. Nature, physics, etc, are truly interesting... no, fascinating. Now if only I had a better grasp of higher level maths and wasn't a Network Engineer (data plumber).

Re:Wow, interesting! by Anonymous Coward · 2010-07-29 01:03 · Score: 0

[theatrical voice] "na-TUUUUUREEEE is AWE!! SOME!!!!"
Re:Wow, interesting! by V!NCENT · 2010-07-29 01:04 · Score: 1

"I would have just assumed it would have gotten "rounder" and possibly larger (elastic) due to centrifugal force"
It does get round and evens out, but due to gravity the evened out band gets pulled down and the resistans on the 'outward ends' all result on a peanut form.
Geez that was mind-bloooooowwwwwiiiiiing.......
So how's the LHC doing?

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Here be signatures
Re:Wow, interesting! by Spad · 2010-07-29 01:16 · Score: 3, Funny

...due to centrifugal force.
My high school physics teacher used to electrocute (With a handheld generator made from a rotary pencil sharpener) people for saying that; also for misspelling accelerate or satellite.
Re:Wow, interesting! by Yetihehe · 2010-07-29 01:25 · Score: 1

Obligatory xkcd link: http://www.xkcd.org/123/

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Re:Wow, interesting! by silentcoder · 2010-07-29 01:29 · Score: 1, Interesting

>>...due to centrifugal force.
>My high school physics teacher used to electrocute (With a handheld generator made from a rotary pencil sharpener) people for saying that; also for misspelling accelerate or satellite.
Yes a common reaction of overzealous highschool teachers - and wrong. Do the math. Forces per se is an oversimplification as it is, useful to model certain aspects of physics, and not for others. Gravitons attract one another, thus is created what we PERCEIVE as the force of gravity if you go down to the quantum level for example.
At the level of Newtonian physics - centrifugal force is as real a force effect as any of the others. True it's a consequence of other forces working together and against each other but it's there nonetheless and it's impact is crucial to predicting how many things will behave.
When two forces work at an angle - the object moves along a (predictable) path created by both forces - it is both correct and useful to model that path as a force in it's own right. At least it OFTEN is, always remember that no scientific model is ideal for EVERY scenario - that's why we don't just HAVE one scientific model.
You want to know how gas will fill a chamber - gravity has so little influence that it's not worth thinking about, quantum mechanics is your friend there. You want to know how it will fill a universe - gravity becomes very important suddenly and this is why the universe does not have it's gases distributed as quantum mechanics would predict, instead of entropy, the universe got decidedly clumpier over time.
For some problems - it's incredibly useful to model centrifugal effects as a force, for others it's much more crucial to work on the shaping forces that create it in the first place - but it's not "wrong" to talk about a centrifugal force if what you want to describe is the effect it causes.

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Unicode killed the ASCII-art *
Re:Wow, interesting! by clone53421 · 2010-07-29 01:30 · Score: 1

Spinning faster = more velocity perpendicular to slope on the leading edge of the loop. It makes sense that it would flatten out.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:Wow, interesting! by XSpud · 2010-07-29 01:30 · Score: 1

If you would have asked me how it would react as it rolled faster and faster, I would have just assumed it would have gotten "rounder" and possibly larger (elastic) due to centrifugal force.
And I'd think for a suitably low coefficient of friction between the band and the ground you'd have been right.
Re:Wow, interesting! by silentcoder · 2010-07-29 01:39 · Score: 1

Also XKCD agrees with me which renders any arguments invalid.

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Unicode killed the ASCII-art *
Re:Wow, interesting! by Anonymous Coward · 2010-07-29 01:49 · Score: 0

My high school physics teacher used to electrocute people for saying that
Killing students seems a bit excessive! Or did you just mean he gave them an electric shock?
Re:Wow, interesting! by VolciMaster · 2010-07-29 01:56 · Score: 1

...due to centrifugal force.
My high school physics teacher used to electrocute (With a handheld generator made from a rotary pencil sharpener) people for saying that; also for misspelling accelerate or satellite.
ah yes... "centrifgual force" - that force applied by a centrifuge.

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antipaucity
Re:Wow, interesting! by ledow · 2010-07-29 02:04 · Score: 4, Interesting

Yes, but then people "weigh" themselves in kg's by standing on a scale that is affected by gravity.
There are certain things that, although "visible" by ordinary people and named, don't actually exist or exist only because we *perceive* them to exist, like that optical illusion with the white triangle that isn't ACTUALLY there.
Centrifugal force may be misnamed (i.e. not a force), it may be incorrect, but it's generally accepted that "a force" exists that has an effect on your when you're spun in a circle. Just because the direction / origin / name of that force is incorrect is no reason to tell people that they're stupid for having felt it and knowing what it is before you explain its origins.
Back in the 60's there was an advertising campaign by scientists working on the behalf of government to target heat loss in elderly people's properties. It encouraged old people to "keep the heat in". It didn't go down well and it took them years to discover why. Eventually it was changed to "keep the cold out" and more elderly people understood that. "Cold" doesn't actually exist, it's just the absence of heat, but old people didn't think that way as easily (and who can blame them? "Shut the door, you're letting the cold in" is a common cry in my family - despite the fact that you're neither letting cold in nor arranging for some mystical "cold" entity to enter your property rather than, say, air with slightly less heat).
There's 100% pedantic accuracy. There's complete bollocks. And somewhere in the middle is how *everybody* thinks, even if they know both extremes in detail.
Re:Wow, interesting! by Seismologist · 2010-07-29 02:28 · Score: 1

Network Engineer (data plumber)
I never understood the whole "engineer" term being attached to everything in IT anyway such as network engineer. I used to work in a role as what can be described nowadays as a "network engineer", but I don't see any of the virtues of engineering applied to this occupation.
Engineering is a profession (a profession in the sense of being a lawyer, doctor, etc. with certification behind it -- as opposed to an occupation such as a plumber) that uses and applies the knowledge of basic engineering principals and math to address practical issues that may have direct consequences to property and the public. Data networking is more of a business problem sort of philosophy.
Now maybe if you were to design a layout of conduits and had to calculate power usage used by equipment, breaker panels, and other things of that nature for a system/installation (such as at a data center), I would certainly consider this to be engineering, and you would most likely be required to apply your PE (professional engineer) stamp as an “electrical engineer” to the design and drawings of said system and NOT as a “network engineer”. I don’t foresee a stamp being used by a “network engineer” unless that engineer happens to be a registered “Professional electrical Engineer”.
Also, be aware that using “engineer” in your title, while not being a certified as engineer (as defined by your State/Provincial department of licensing) is just as misleading as saying you’re a network doctor, or network lawyer. The title PE, or Professional Engineer, is a registered trademark in the US.
The term “engineer” in any title in Canada is regarded as a trademark. This got Microsoft into trouble in Canada when they were offering “MS engineering certificates”. There is a Wikipedia entry (en.wikipedia.org/wiki/Controversies_over_the_term_Engineer) about this all this as well well.
Now network researcher, network scientist, network analyst, these are all more appropriate title to the occupation.

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~ In Trust, We Trust ~
Re:Wow, interesting! by rotide · 2010-07-29 02:47 · Score: 1

Contact my boss and HR to have my title changed to meet your, apparently, delicate sensibilities. Either that, or get off your high horse and stop complaining about arbitrary job titles that change at the mere whim of the aforementioned persons.
Or, to put it another way, stop being so damn pedantic. I've honestly never seen a rant so serious about something so meaningless.
Re:Wow, interesting! by Anonymous Coward · 2010-07-29 03:11 · Score: 0

What do you call the person who drives a train?
Re:Wow, interesting! by Anonymous Coward · 2010-07-29 03:18 · Score: 0

It's still long and hard...
Re:Wow, interesting! by Twinbee · 2010-07-29 03:26 · Score: 1

Even on a pedantic level though, it's correct to say something's colder *relative* to something else, rather than as an absolute level of cold. Also bear in mind that they're talking about the sensation/feeling of cold rather than its physical makeup. On a certain level, red is best spoken about by its name rather than its wavelength. It's just a different kind of pedantic-ness, not necessarily less pedantic.

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Why OpalCalc is the best Windows calc
Re:Wow, interesting! by Guignol · 2010-07-29 03:42 · Score: 1

The overzalots teachers are right and misquoted.
When they say 'there is no centrifugal force but instead a centripetal force' they don't say it our of nowhere at any time just to hurt your feelings
Whenever a child get in school starting to learn basic physics, he almost always 'know' about the so called 'centrifugal force' meaning the force you experience when you are in a rotating wheel, orthe force that will prevent the water from falling in a fast rotating bucket attached to a rope (etc.)
So the teacher will rightly say that the observed effect is not due to any centrifugal force, and indeed it could not be modelled so, the only 'force' is centripetal (right of course it has its reaction) but what the children 'feel' and attribute to a centrifugal force is in fact inertia which by the way is not centrifugal since as soon as the centripetal force will cease the inertia will lend the mobile to follow a tangential trajectory
Of course you can still confront magnets or electrical charges to show that there are indeed such things as centrifugal forces but it has nothing to do with the 'evil stupid teachers' arguments when they want to make a point about the centripetal vs centrifugal force
Re:Wow, interesting! by FrigBot · 2010-07-29 03:57 · Score: 1

In Canada we take this especially seriously, and our provincial associations will go so far as to take a usurper of the term "engineer" to court to require them to change their title. The bottom line is that the public is meant to know that they can trust the professionalism and competency of a real engineer. You count on us to design things which will be safe. And to claim you are an engineer (network, petroleum transfer, etc.) is misleading to the public in the sense that you understand the ramifications of that public trust in doing your work. It's not meaningless.
And to the hoser below, regarding train engineers (drivers), they are specially exempted because it is a time-honoured tradition for them to be called engineers, and everyone knows what it means, so there's no problem there. Thus we can call them engineers, and we all know that it doesn't mean quite the same thing as a professional engineer. Unless they have an engineering degree.
Re:Wow, interesting! by rotide · 2010-07-29 04:11 · Score: 1

"It's not meaningless."
In Canada.
For those not in Canada, ignore the preceding posts except to understand the social differences in terminology and/or Title usage. But for the sake of my original post, it most certainly is meaningless except to show that I am not a physicist or in a related field.
Also interesting to note however, the understanding of the Canadian ramifications of the title "Engineer" apparently has nothing to do with basic reading comprehension and understanding basic context.
It was an interesting diversion though, even if entirely OT and _extremely_ pedantic.
Re:Wow, interesting! by PiSkyHi · 2010-07-29 04:19 · Score: 1

falling on you.
Re:Wow, interesting! by electrostatic · 2010-07-29 04:27 · Score: 2, Interesting

"Spinning faster = more velocity perpendicular to slope on the leading edge of the loop. It makes sense that it would flatten out."

Very good point. The back edge of the loop is being accelerated perpendicularly upward. IOW, the small length of rubber that's breaking contact with the table is yanked -- accelerated -- upward to a high vertical velocity. Therefore, it will rise higher that it does at a slower rolling speed. Like throwing a ball upward with a high velocity against gravity, it reaches a higher distance. In the case of the rubber loop the restoring force is tension in the rubber just ahead of the peak.

But there's that difficult-to-model problem of elasticity. I imagine the fast-rising rubber is pulled downward by tension in the bit of rubber just ahead of the highest point. Most of its upward momentum is opposed by the force of that stretched bit. And the kinetic energy, which is proportional to the square of the velocity, is transferred to mechanical energy (force X distance) stored in the stretched bit. Since KE is non-linear (square of velocity) you often get unexpected behavior. Here we get into differential equations!

Regarding the role of elasticity in the transfer of momentum and kinetic energy in the shaping of the rolling loop, it would be interesting to do an experiment using a non-elastic loop. An example would be a metallic chain. I expect the shape would be different.
Re:Wow, interesting! by socrplayr813 · 2010-07-29 04:59 · Score: 1

I was going to just mod GP up, but I feel like typing:

Contact my boss and HR to have my title changed to meet your, apparently, delicate sensibilities. Either that, or get off your high horse and stop complaining about arbitrary job titles that change at the mere whim of the aforementioned persons.
Or, to put it another way, stop being so damn pedantic. I've honestly never seen a rant so serious about something so meaningless.
Well, no, this has nothing to do with being pedantic. The meaning of the word 'engineer' has been diluted. Any schmuck with a bit of common sense and a computer can learn to be a 'computer engineer' or whatever silly, meaningless title you feel like making up. It only got to be like that because people wanted to make boring jobs sound better than they actually were. This doesn't necessarily apply to you because I don't know what your job is, but people should suck it up and be realistic about what their job is.
I spent my time, money, and a HELL of a lot of effort to become a REAL engineer. That should mean something. It USED to mean something. People don't walk around calling themselves doctors and lawyers without the degrees/certifications/whatever. I'm not about to start writing letters or what have you, but GP makes a good point. It should not be dismissed just because you want to feel important when you tell people what your job is.

--
The confidence of ignorance will always overcome the indecision of knowledge.
Re:Wow, interesting! by russotto · 2010-07-29 05:05 · Score: 1

Engineering is a profession (a profession in the sense of being a lawyer, doctor, etc. with certification behind it -- as opposed to an occupation such as a plumber)
There were doctors, lawyers, and engineers before there were certifications for same. And certifications are required for plumbers in most jurisdictions. Being blessed by the bureaucracy doesn't make you an engineer, and not being so blessed doesn't make you not one.
Re:Wow, interesting! by Albatrosses · 2010-07-29 05:15 · Score: 1

At my (Canadian) University, our Engineering Students' Society sells t-shirts that say "I get to drive a train!"
Re:Wow, interesting! by silentcoder · 2010-07-29 05:15 · Score: 1

You know we all also learned the right-hand law for electromagnetic inference and that ALSO disapears if the objects stop moving ... does that mean we can't model magnetic forces now ?

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Unicode killed the ASCII-art *
Re:Wow, interesting! by Guignol · 2010-07-29 05:28 · Score: 1

Sorry I don't see your point (and I am not saying this in a way that would try to diminish it (really this is not an agressive answer in any way), I just don't see what you mean as far as my point is concerned)
Re:Wow, interesting! by rotide · 2010-07-29 05:39 · Score: 1

Irrelevant.
Human Resources states my title as "Network Engineer". So that's what I posted. And for the record, it wasn't posted for vanities sake. It was to show that I'm not a physicist. Plain and simple.
It seems you want me to make up my own title in lieu of the one HR gives me. I guess I could have made it up to something like "Internetworking tubes maker and cleaner as well as designer dude".
Wouldn't have changed a damn thing with regards to my original post.
And yes, nitpicking about job titles when the title itself had little to nothing to do with the post and drumming on about the meaning of the word "Engineer" was entirely out of context and entirely pedantic.
Re:Wow, interesting! by silentcoder · 2010-07-29 05:48 · Score: 1

You stated that we cannot model centrifugal force because it disappears if the component forces are removed (duh- remove either of them and there is no longer anything to add up to it).
I pointed out how you can have forces created by other forces that aren't even directly part of them (you need a force to move a conductor through a magnetic field) and since we have no problem modeling those and predicting exactly what will happen if the motive force is removed - this has nothing to do with the usefulness of sometimes modeling centripetal effects as if it was a motive force in it's own right - especially since, in some (admittedly more esoteric) cases, it is.
The suggestion that you cannot teach the esoteric cases to the smart kids because it would confuse the dumb ones I have heard about every subject a million times and having BEEN one of the bored and frustrated smart kids I have only one response: balderdash.

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Unicode killed the ASCII-art *
Re:Wow, interesting! by Chris+Burke · 2010-07-29 06:34 · Score: 2, Insightful

Yeah, stupid meteorologists, talking about "cold fronts". No such thing! They should say "Fronts containing less heat." But then again all fronts contain heat, so what's a warm front? It's just warm compared to cold fronts.
Maybe it's because of my electrical engineering schooling and years spent acting as if it was the positive charge carriers that were moving, but I don't see any problem with saying "let the cold in". Cold is a negative heat delta. Big whoop. When you open the door in the winter, cold air blasts you in the face, cold air got in the house, and the house becomes colder. You let the cold in.
"Cold" may not exist but the concept is valid, and you can only tell the difference because of absolute zero. It's very similar to negative energy, a common concept in physics. The question of whether or not it "exists" vs is a valid way to conceptualize energies that only average to zero, is just how you view it.
There are legitimate contexts where it is 100% pedantically accurate to talk about things that don't exist.

--

The enemies of Democracy are
Re:Wow, interesting! by secondbase · 2010-07-29 06:47 · Score: 1

I agree completely: this is exactly the sort of experiment that helps all kinds of simulations be more accurate, and makes predictions that may not be testable more likely to be correct.

This kind of thing is also why I always distrust the stories (evolutionary psychologists are the worst offenders) given by scientists instead of experiments: "It's logical that people who helped each other would be more successful, so they reproduced more often...." But logical is often disproved by experiment, so if it hasn't been tested, it's a guess.
Re:Wow, interesting! by Guignol · 2010-07-29 06:55 · Score: 1

Oh right, thanks for your answer
I didn't "state it" that's giving much more strenght thant what I meant as it was in fact not my point at all
but thanks for your answer, I see how you interpreted it.
My point was not on this part, that's a separate thing to debate on I don't completely agree with what I wrote per se, it was just part of the main point
To me the point was that I don't like physics teachers being 'ridiculed' (so to speak) around the centripetal/centrifugal force argument because
- I see it out of context (as far as the teachers argument is concerned)
- it is not even right, I mean, teachers are right (as far as I kno/am concerned) - to me the argument appears when trying to explain what inertia is in this case vs the 'magic centrifugal force'

Maybe this is something personal, of course, you never know, but it has always be clear to me, before studying physics (as achild at school, I am not talking about graduate level matters) I was shown by my grand-father and my father "how the centrifugal force works"
So when I got a better explanation of the phenomenon I bought the 'cebtripetal vs centrifugal' argument, you know, not that I don't understand you can model it any way you want, just as you could model an accelerating frame as a galilean frame with a force or just as you could say there is no difference between a gravitational pull on the referential and this frame being accelerated.
Anyway my point (and I probably shouldn't have detailed the part that you focused on which were poorly worded becasue my focus was on something else) was that I really don't apreciate physics teachers being ridicules out of context when they teach something very valuable arguaing against centrifugal force to let you inderstand about inertia
Re:Wow, interesting! by JustABlitheringIdiot · 2010-07-29 07:25 · Score: 1

Back in the 60's there was an advertising campaign by scientists working on the behalf of government to target heat loss in elderly people's properties. It encouraged old people to "keep the heat in". It didn't go down well and it took them years to discover why. Eventually it was changed to "keep the cold out" and more elderly people understood that. "Cold" doesn't actually exist, it's just the absence of heat, but old people didn't think that way as easily (and who can blame them? "Shut the door, you're letting the cold in" is a common cry in my family - despite the fact that you're neither letting cold in nor arranging for some mystical "cold" entity to enter your property rather than, say, air with slightly less heat).
*Emphasis mine*
So I have to ask where geographically that was. Chalk it up to nothing but curiosity, but it is the exact opposite of what I heard growing up in the northeast "Close the door, you're letting all the heat out. I'm not paying to heat the backyard".
Re:Wow, interesting! by silentcoder · 2010-07-29 07:30 · Score: 1

I have no problem with the point you make - my problem is with those teachers who when the smarter kids can USEFULLY model it as a force to solve problems quicker (fully understanding what's REALLY happening - that inertia is an effect of momentum is an effect of mass- maybe even know the Einsteinian addition that allows some things to have momentum WITHOUT having mass like photons) get punished for taking what to THEM is just a clever shortcut.
Clever shortcuts are a fundamental trick to being better things- it's a problem if you ONLY know the shortcut and not the road that led to it - then it's just an error. The problem is that our schoolsystem makes no differentiation between the kids who just know what their grandparents taught them (although my dad was an engineer who taught me that centrifugal "force" in those cases isn't really a force, it's just a useful way to calculate the result of Newtons first law on something forced by a constraint to travel in a circular pattern) and the kids who think the simplified surface answer is the whole answer.
That's why it's those smart kids who later complain about it... we feel we could have gotten further along the path if we were allowed to use shortcuts to skip over those things. We already understood them, doing the sums a thousand times over when there's a quicker way to get the same result by pretending there's another force is CLEVER - not stupid.
Mind you most of school science is all still just the bare scratchings of the surface. Everybody who did it knows that prisms split light up and this causes rainbows... but how many of us really know the COOL part of that question ?
How do thousands of drops combine into one big rainbow ... and for that matter - why is it bow-shaped ? The real geometry of how rainbows form is gorgeously ellegant... the colours are, quite frankly, the boring bit.

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Unicode killed the ASCII-art *
Re:Wow, interesting! by Anonymous Coward · 2010-07-29 07:59 · Score: 0

Electrocute means to kill with electric shock. Non-fatal shocks are just called shocks.
I'm not saying you're wrong though. I'm sure your teacher killed many students.
Re:Wow, interesting! by Guignol · 2010-07-29 08:15 · Score: 1

(?)
alright, I don't see why you put so much emphasis on bad teachers not understanding how their gifted students get it so much better than themselves
Either you are no as stmart as you remotely think you are, or you had a terrible school experience and in this case you should get over it
But how should I know ? I am not a physics teacher (I wish) I am not a smart kid (I wish)
I just witnessed that students not really getting the whole of it would make fun of physics teachers that made a good point of explaining (or trying to) how inertia plays and what is has to do in the 'centripetal/centrifugal' argument
I think in the end it is more snobism than anything ele driving the argument, but however you look at it, there is indeed no such thing as a centrifugal force (when it is in fact a felt effect of inertia)
I remeber being exited as understanding why it was so, I also understand how it can be made a point "against it" (model, blahblah), but come on... WTF with your smart kids rant ?
Re:Wow, interesting! by clone53421 · 2010-07-29 08:34 · Score: 1

There are not two forces, though. There is the object’s velocity (which is not a force but rather an inertia) going in one direction, and there is a force acting upon the object (which accelerates the object... i.e. produces a velocity component normal to its current line of motion).
Now, if you want to talk about adding the velocity vectors and creating a new vector to describe the object’s motion, we’re A-ok.

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:Wow, interesting! by rdnetto · 2010-07-29 18:30 · Score: 1

My high school physics teacher used to electrocute (With a handheld generator made from a rotary pencil sharpener) people for saying that; also for misspelling accelerate or satellite.
Yes a common reaction of overzealous highschool teachers
Exactly which high school did you go to?

--
Most human behaviour can be explained in terms of identity.
Re:Wow, interesting! by silentcoder · 2010-07-29 19:51 · Score: 1

You didn't get to go to school in South Africa under the apartheid system. School was little more than a political indoctrination system and conformity above all was the value they tried to impress upon us. Critical questions were punished...
So if it answers your questions: I was a straight A student in the subjects with good teachers, and failed subjects with bad ones - some of which I went on to be a top student of at University - and one of which forms a cornerstone of my career...
The first experience I had of this happened in my very first year of high school - we were doing a course on electricity and the teacher said what the textbook said: "100volts and higher are dangerous", I raised my hand and said: "Well depends on context surely - directly to the blood stream - 1 volt is more than enough to kill you".
The teacher looked at me and said "Oh shut up, 1v can't harm anybody under any conditions". I politely said "My father is an electrical engineer- he designed the powergrids for half the cities in this country* - and he wrote his thesis on electrical safety designs with a study of it's interaction with the human body.**"
I didn't get to finish my sentence - I received corporal punishment right there for "being disrespectful" (which was a phrase meaning: daring to disagree with authority"
That was the school experience I had. By all means - I am completely over it, I has no impact on my life today. But I also have a social conscience - I know that the attitude in most schools is still exactly the same and I care about the kids going through the same - I care about the impact it has on society. I know too many people who had the intelligence to do groundbreaking things but never even made it to university because schools broke their spirit. I know how many kids will get HIV infections today because schools think telling them about the existence of condoms will encourage them to have sex (they already are, but now their not doing it safely - but those kinds of teachers would much rather pretend they don't).
*After 1994 most of the former "black" cities didn't have power - the government spent a lot of money on providing them with electricity, my dad's company had most of the design contracts for that and he was in charge of most of those design projects.
**If you care - the reason is that the nervous system uses electricity. Electrical pulses from the brain to the heart controls it's beat. A voltage from outside that's high enough to overcome the resistance of the blood and provide a current stronger than the current of the nervous system afterward will effectively "override" it. DC causes an instant flat-line, AC sends the hearth rhythm out of whack (neither 50 nor 60 Herz is anywhere near normal) - either way, instant heart-attack. Considering all the factors including the average resistance of human blood and the current of the human nervous system - 1volt is more than enough. The reason it usually doesn't kill people is because the human skin has a very high electrical resistance and most electrical shocks end up running over it rather than through our bodies (effectively conducted by hair and sweat)- at worst causing muscle spasms by messing with the nerve signals (through induction). Most electrical shock deaths actually happen because voltage over a high-resistance conductor produces a lot of heat - it burns through the skin, and only then - once it's running through the (low resistance) blood does it kill you.

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Unicode killed the ASCII-art *

Brakes, please. Please? by Kupfernigk · 2010-07-29 01:11 · Score: 4, Informative

I'm sorry but this is such a common mis-spelling on Slashdot that it's getting to me. Cars have brakes. "Car breaks" means it stops working because of mechanical or electrical failure. Spellcheckers can't fix homophones.

--
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."

Re:Brakes, please. Please? by Anonymous Coward · 2010-07-29 01:14 · Score: 4, Funny

Spellcheckers can't fix homophones.
I can tell you have your spellchecker on, though I think you ment to write "homophobes".
I too believe they should be fixed.
Re:Brakes, please. Please? by Anonymous Coward · 2010-07-29 01:22 · Score: 0

But what if he drives it into something? You're definitely breaking the car, and applying the breaks at the same time. Unless you're one of those Toyota "drivers", then braking definitely doesn't apply.
Re:Brakes, please. Please? by Bromskloss · 2010-07-29 01:48 · Score: 3, Funny

Cars have brakes. "Car breaks" means it stops working because of mechanical or electrical failure.
I honestly thought he was talking about car crashes and even though that was a strange way of saying it, I convinced myselft that is was physically sound.

--
Swedish plasma phys. PhD student; MSc EE; knows maths, programming, electronics; finance interest; seeks opportunities
Re:Brakes, please. Please? by Anonymous Coward · 2010-07-29 01:50 · Score: 0

I'm right with you, but I think it's time to tie my t-shirt to a stick. I have a picture of a Mercedes TV commercial from BBC America, which has bold white type saying 'AUTOMATIC EMERGENCY BREAKING' right across the screen.
If Mercedes can't get it right, we may as well give up on Slashdot.
Re:Brakes, please. Please? by ledow · 2010-07-29 02:12 · Score: 1

While we're at it, can someone please bring up the following:
to/too/two
there/they're/their
your/you're
whose/who's
God, I know I'm pedantic but how hard is it to get *simple* things like this right? At least most of the time.
It severely hinders my reading speed if some text has simple mistakes like that. My mind jars as it hits them and slows me down.
Re:Brakes, please. Please? by Anonymous Coward · 2010-07-29 02:37 · Score: 2, Funny

Tell that to two Slashdot users whose who's are wrong too. They're messing up their you'res while your there's are perfect.
Re:Brakes, please. Please? by Guignol · 2010-07-29 02:44 · Score: 1

Thank's I would of right it so my self but you bit me to eat.
I guess its fine I should of been more fasterer
Re:Brakes, please. Please? by simcop2387 · 2010-07-29 02:46 · Score: 0, Troll

don't forget about the other three!
you/yew/ewe!
Re:Brakes, please. Please? by Anonymous Coward · 2010-07-29 02:48 · Score: 0

There is no hyphen in the word "misspelling."
Re:Brakes, please. Please? by Guysmiley777 · 2010-07-29 02:54 · Score: 1

How about "begs the question" used as "raises the question"? I know it's a lost cause but it still causes my eye to twitch.

--
Coding with assembly is like playing with Legos. Coding an application in assembly is like building a car with Legos.
Re:Brakes, please. Please? by clone53421 · 2010-07-29 02:57 · Score: 1

There can be.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:Brakes, please. Please? by Anonymous Coward · 2010-07-29 03:04 · Score: 0

Miss Pelling was recently wedded to Mr. Don T. Grammer.
Re:Brakes, please. Please? by Twinbee · 2010-07-29 03:08 · Score: 1

I was going to moan at you that it was obvious from the context that he meant 'brakes', but then someone goes and replies to you and thought he really did mean 'break'. Sigh... I was really going to enjoy the moan too ;)

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Why OpalCalc is the best Windows calc
Re:Brakes, please. Please? by egomaniac · 2010-07-29 03:11 · Score: 1

I think you're on the wrong side of this one, obviously. Words and expressions change meaning over time, and at this point you might as well be upset over the fact that people use the word "computer" to mean "electronic calculating device" instead of its original meaning, "a person who performs tedious calculations by hand".
It's time to give up and accept that you have lost the fight. "Begs the question" now means "raises the question".

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ZFS: because love is never having to say fsck
Re:Brakes, please. Please? by quadrox · 2010-07-29 03:47 · Score: 1

Even worse, my mind has started to "crash" on rare occasions when people write "could have" instead of "could of" and similar stuff, simply because it is so rare to see it spelled right nowadays. That's really messed up.
Re:Brakes, please. Please? by allusionist · 2010-07-29 03:54 · Score: 1

You mean "whose whos" not "whose who's" and "your theres" not "your there's." Stop abusing the poor apostrophe by needlessly jamming it into plural nouns.
Re:Brakes, please. Please? by boxwood · 2010-07-29 03:58 · Score: 3, Funny

a bit of tape stuck over the bottom left corner can fix a homophone.
Re:Brakes, please. Please? by PiSkyHi · 2010-07-29 04:11 · Score: 2, Funny

I think the key to this is that when a car brayx, it slows down and will eventually stop moving.
Re:Brakes, please. Please? by oldmac31310 · 2010-07-29 04:33 · Score: 1

Now I'm really confused.

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http://www.acetonestudio.com
Re:Brakes, please. Please? by mhajicek · 2010-07-29 04:41 · Score: 1

One of my pet peeves: "Less" vs. "Fewer". You can have "fewer people" under normal circumstances, but if you have "less people" it implies that they've been mashed up to the point you can't tell where one ends and the other begins, like oatmeal.
Re:Brakes, please. Please? by Dagger2 · 2010-07-29 06:05 · Score: 1

And the non-plural nouns, please. I've seen "get's" and "let's" here recently.
It's like people see an s coming up in the sentence and instinctively start mashing the ' key.
Re:Brakes, please. Please? by gnola14 · 2010-07-29 07:20 · Score: 1

how about than vs then? I see that A LOT...
Re:Brakes, please. Please? by Anonymous Coward · 2010-07-29 08:48 · Score: 0

You've forgotten the worst of the not quite homophone roadblocks:
have/of
Re:Brakes, please. Please? by Anonymous Coward · 2010-07-29 09:55 · Score: 0

I too believe they should be fixed.
And by fixed, he doesn't mean "repaired", more like when your cat or dog is "fixed".
Re:Brakes, please. Please? by jc42 · 2010-07-29 15:08 · Score: 1

One of my pet peeves: "Less" vs. "Fewer".
You're on the losing side of that language change. Too many people are being taught math these days, and mathematical terminology pretty much uses "less [than]" for all numeric comparisons, regardless of the English count/mass classification. The math world simply isn't going to listen to this particular peeve, and will continue to teach people to use "less" for any numerical comparison.
Actually, if you dig into the history of the topic, you'll find that "less" has been used this way pretty much since the language has been called "English". The less/fewer distinction is a bogus modern peeve, invented by people wanting to impose a distinction that the language has never made.

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Those who do study history are doomed to stand helplessly by while everyone else repeats it.
Re:Brakes, please. Please? by Anonymous Coward · 2010-07-30 02:16 · Score: 0

how about than vs then? I see that ALOT...

FTFY
Re:Brakes, please. Please? by Anonymous Coward · 2010-07-30 02:25 · Score: 0

same difference. anyways, it begs the question whether I couldn't care less about her's.
Re:Brakes, please. Please? by Muad'Dave · 2010-07-30 04:52 · Score: 1

You forgot lose/loose. That one can be funny, as in "I don't want them too loose there lunch!" or "Your about two loose you're sanity."

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Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
Re:Brakes, please. Please? by Bromskloss · 2010-07-30 07:11 · Score: 1

I convinced myselft that is was physically sound.
I wasn't referring to the sound energy a car emits when it crashes, but maybe I should have.

--
Swedish plasma phys. PhD student; MSc EE; knows maths, programming, electronics; finance interest; seeks opportunities
Re:Brakes, please. Please? by Anonymous Coward · 2010-07-30 18:48 · Score: 0

Ok, that's to much. I'm tired of grammar nazis and all they're crap. Two often someone makes a simple spelling mistake and then their paying for not proofreading there work. Life is to short too waste time on such things. Who's right is it too tell someone else whose right or wrong when it comes to grammar? Maybe your the one who doesn't no you're p's from you're q's!!!

model by Anonymous Coward · 2010-07-29 01:13 · Score: 0

>> researchers know exactly what forces act on a ball rolling down an incline

No they dont, they just think they have a good working model.

How do you make it interesting to students by dimethylxanthine · 2010-07-29 01:17 · Score: 0

Rolling rubber band, Faster!, squashed, ball, acceleration... Finally, some sex in the realm of physics! If only my physics (and math!) books had this many innuendos on one page...

centrifugal forces by StripedCow · 2010-07-29 01:17 · Score: 1

However, if the rubber band is spinning really fast, aren't the centrifugal forces pushing the band outward, compensating the squashing?

Disclaimer: I didn't RTFA.

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If Pandora's box is destined to be opened, *I* want to be the one to open it.

Re:centrifugal forces by talz13 · 2010-07-29 01:29 · Score: 1

It's the centripetal forces that are pulling the band towards the center, there is no force pushing the band outwards (the band really just wants to keep going in a straight line, but can't due to the force pulling it inwards). It is easier to illustrate with the weight being swung in a circle attached to the end of a string, where the string is providing the inward force.
Re:centrifugal forces by clone53421 · 2010-07-29 01:33 · Score: 1

Centrifugal force doesn’t exist. It is simply our perception of momentum in a spinning object.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:centrifugal forces by Culture20 · 2010-07-29 01:35 · Score: 1

However, if the rubber band is spinning really fast, aren't the centrifugal forces pushing the band outward, compensating the squashing?
You also didn't read your physics book. There is no such thing as centrifugal force (outward from center).
Re:centrifugal forces by StripedCow · 2010-07-29 01:37 · Score: 1

Yes, of course the centripetal force is the opposite of the (fictitious) centrifugal force in Newton's third law.

--
If Pandora's box is destined to be opened, *I* want to be the one to open it.
Re:centrifugal forces by StripedCow · 2010-07-29 01:39 · Score: 1

Forces do not exist. They are simply our perception and our way of modeling certain aspects in nature. Centrifigal forces are simply a way of referring to the opposite of centripetal forces (in Newton's third law).
But that was entirely not the point.

--
If Pandora's box is destined to be opened, *I* want to be the one to open it.
Re:centrifugal forces by flaco629 · 2010-07-29 01:46 · Score: 1

Centrifugal forces don't exist. They are fictional forces used to make non-inertial frames of reference conform to Newton's laws. So they aren't going to compensate for much of anything.
Re:centrifugal forces by clone53421 · 2010-07-29 01:50 · Score: 1

So what you are saying is, centrifugal force is the equal and opposite force to the force you must apply to move a rotating system’s centre of mass.
No... that’s simply its momentum. Or its inertia, as they are the same thing.

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.

Direct link to the .FLV by Anonymous Coward · 2010-07-29 01:20 · Score: 3, Informative

For those of us where the player won't launch when you click "play video" in the article, here's a direct link to the flash video:

http://sciencevideo.aaas.org/sciencenow/snow_ribbon_250.flv (320x240, 17 seconds, 1.1MB)

Re:Direct link to the .FLV by dborod · 2010-07-29 03:57 · Score: 1

Thanks. I wonder why the video wouldn't play for me on the site?

LOL by Anonymous Coward · 2010-07-29 01:22 · Score: 0

Fascist.

Re:LOL by Geotopia · 2010-07-30 09:14 · Score: 1

Homeopath!

This requires a government study by countertrolling · 2010-07-29 01:23 · Score: 1

Similar to the one done to determine the flow rate of ketchup...

--
For justice, we must go to Don Corleone

Re:This requires a government study by Anonymous Coward · 2010-07-29 01:33 · Score: 0

yea I know, its basic high school science, and we paid researchers to tell us that?
9th grade science 101 has centripetal force in it

This requires Yakety Sax by cangrande · 2010-07-29 01:37 · Score: 5, Funny

All science videos are improved by Yakety Sax.

Miracle by JustOK · 2010-07-29 01:40 · Score: 5, Funny

Fucking rubber bands, how do they work?

--
rewriting history since 2109

Re:Miracle by TapeCutter · 2010-07-29 03:08 · Score: 1

"Fucking rubber bands, how do they work?

Feynman to the rescue.

The phenomena in TFA is just begging for a numerical simulation. I wonder if something like Blender or PhysX would predict this behaviour correctly?

--
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Re:Miracle by JustOK · 2010-07-29 04:32 · Score: 1

And I don't wanna talk to a scientist
Y'all motherfuckers lying, and getting me pissed

--
rewriting history since 2109
Re:Miracle by JustABlitheringIdiot · 2010-07-29 07:28 · Score: 1

Fucking rubber bands, how do they work?
I don't know, like magnets we will probably never know.

Makes perfect sense. by clone53421 · 2010-07-29 01:43 · Score: 1

It’s all about the deformability of the loop. In a perfectly circular loop, the intersection with the ground is tangential. If the loop deforms, it strikes the ground rather than intersecting tangentially, and the faster it spins, the harder it hits the ground. The harder it hits, the more it deforms.

Alternately, as I see it, if it is accelerating due to its friction with the ground (i.e. if you spin it up first and then let it go) it should be able to temporarily keep itself supported under its own momentum, but as soon as that friction drops to zero it will begin to collapse due to its own weight and then the above will apply. As long as the frictional force vector is zero or points backward, the band should deform. Naturally I’ll be needing a few hundred thousand dollars to be testing my theory.

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.

Re:Makes perfect sense. by pz · 2010-07-29 02:12 · Score: 1

It’s all about the deformability of the loop. In a perfectly circular loop, the intersection with the ground is tangential. If the loop deforms, it strikes the ground rather than intersecting tangentially, and the faster it spins, the harder it hits the ground. The harder it hits, the more it deforms.
Alternately, as I see it, if it is accelerating due to its friction with the ground (i.e. if you spin it up first and then let it go) it should be able to temporarily keep itself supported under its own momentum, but as soon as that friction drops to zero it will begin to collapse due to its own weight and then the above will apply. As long as the frictional force vector is zero or points backward, the band should deform. Naturally I’ll be needing a few hundred thousand dollars to be testing my theory.
Just watch a little top fuel drag racing to see tire (a/k/a elastic loop) deformation under load.

--

Put my fist through my alarm clock with its ding-dong death inside my ear. - The Blackjacks.
Re:Makes perfect sense. by clone53421 · 2010-07-29 02:19 · Score: 1

One could do that; however I do not think they are a very good subject to study this effect. They are moving too quickly to observe very well without high-speed camera equipment, heavily loaded (apart from their own weight), and designed to deform as little as possible under smooth conditions because tire deformation increases the drag on the vehicle (remember that over-inflating your tires will increase your gas mileage?).

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:Makes perfect sense. by Anonymous Coward · 2010-07-29 04:29 · Score: 0

One could do that; however I do not think they are a very good subject to study this effect. They are moving too quickly to observe very well without high-speed camera equipment, heavily loaded (apart from their own weight), and designed to deform as little as possible under smooth conditions because tire deformation increases the drag on the vehicle (remember that over-inflating your tires will increase your gas mileage?).
Not really how/why they are designed the way they are.
The reason they are 70% tire and 30% wheel is because they WANT them to deform on launch. As the tire material piles up on the road the contact patch between the tire and the road increases, giving the tire more traction. Once the initial acceleration of the vehicle is over, the CENTRIFUGAL force acting on the tire causes it to expand outward, decreasing the contact patch, but at the same time decreasing the drag and rolling resistance. This is allowed to occur at higher speeds because the available power being put into the tire is not enough to cause the tire to spin against the ground, losing the benefit of static friction.
Re:Makes perfect sense. by SleazyRidr · 2010-07-29 05:38 · Score: 1

It makes me wonder if this could all have been achieved by sitting down and working it all out from fundamental laws. It seems like it could have, although the experimental approach was probably faster!

--
Is 1563649 a prime number?

Is this valid, spinning inside another wheel? by guidryp · 2010-07-29 01:58 · Score: 1

Won't there be Centrifugal/Centripetal forces from the drive wheel it is running inside?

Or do these forces not exist because the rubber band is essentially stable in it's position inside the wheel?

Re:Is this valid, spinning inside another wheel? by minogully · 2010-07-29 02:09 · Score: 1

Yeah, the first thing I thought when I saw this, is, the surface that the rubber band is rolling on is curved inwards! I thought they were studying the movement of it rolling down a hill... I wonder if there are any significant differences between the behaviour of this experiment vs. the behaviour of a rubber band rolling along a tilted conveyor belt? What about a surface curved in the other direction?
Re:Is this valid, spinning inside another wheel? by Scatterplot · 2010-07-29 02:24 · Score: 1

As some of the other posters have said, since "centrifugal" forces "technically don't exist" then no. What is perceived as centrifugal force is really the momentum of an object being acted on by the rotating vessel (in this case it would be the wall of the container). So while the rim experiences forces that look like forces pulling it to the center, the rubber band would not, since it's not rotating. However, the rubber band *itself* is rotating, so internally there would be "centrifugal" forces, which is where the peanut shape comes from.
Re:Is this valid, spinning inside another wheel? by Anonymous Coward · 2010-07-29 03:03 · Score: 0

I thought the same thing, I think this is an extremely flawed experiment which proves nothing. The centripetal force of the hamster wheel on steroids is simply forcing the middle of the rubber band towards the wall of the wheel and the edges have more structure to resist the force. I was intrigued until I saw the video, completely worthless.
Re:Is this valid, spinning inside another wheel? by minogully · 2010-08-05 06:23 · Score: 1

I don't think there's much centripetal force on the rubber band as a result of the rotation of the drum. I think that only happens when the band can't roll at the right speed to maintain its position in the drum.

I'm not saying there isn't centripetal force though. I would expect there to be centripetal force expanding the band because it itself is spinning. Obviously, it's not enough to counteract the other forces.

I'm not a Physicist, though, so I could be wrong.

Isn't the center of a golf ball a rubberband ball? by realsilly · 2010-07-29 02:04 · Score: 1

Ok so if I remember correctly, the center of a golf ball is made with a rubberband like substance, and then is covered with that nice hard plastic shell. But as a golf ball lands and rolls, wouldn't that spin cause the same reaction as what is in that video? Or could we assume that it is so tightly wound and then encased with little to no wiggle room that this alteration of shape would not take place? I'm thinking it's the latter.

Next I'd love to see the same thing performed with the traditional egg drop experiment and how long the egg would last.

--
Life takes interesting turns, but the most interest is when you're off the beaten path.

Why can't we model this? by CrazeeCracker · 2010-07-29 02:15 · Score: 1

Every time I hear of a story similar to this one, I'm reminded of something that has always puzzled me:

We are aware of all the (relevant) forces at work in and on the rubber band. At a sensible scale, for all intents and purposes, we could say we understand the rubber band perfectly. (Right?)
So the only thing holding us back from modelling this kind of stuff is computational resources, which, I would assume, should not be that much of a problem with today's supercomputers. (Right? I mean it doesn't have to be in real time.)
So why aren't we doing it? In Physics we deal with equations that involve approximations a lot of the time, but that's more out of convenience and simplicity than out of a lack of understanding of our world (again, at a scale where we can use classical physics).
Take thermodynamics. Or fluid dynamics. They're both just approximations of atoms interacting in a way that is very much understood already, but we keep them around because it's easier to imagine the physical implications of a concept like temperature or drag force, rather than millions upon millions of tiny particles bouncing around semi-randomly.

I guess my point is, if they can have virtual wind tunnels, why can't they have virtual rubber bands? As a matter of fact, why can't we calculate the properties and interactions of a significant fraction of the things around us without the need for experiment?

--
Of course I didn't RTFA.

Re:Why can't we model this? by painandgreed · 2010-07-29 09:09 · Score: 1

So why aren't we doing it?
Simple answer is because it is usually cheaper, quicker, and more reliable to actually perform the experiment in meat space and list the results in a chart for reference when needed by engineers.
If you look at your assumption that the only thing holding us back is computational resource, understand that this also includes programing the problems to begin with. Even if the physicists have come up with all the correct equations and variables, then they have to be programmed into code. Some of those equations are going to be fairly difficult differential equations that might not even be solvable. There are various ways to use numerical methods to approximate this but it just adds another layer of complexity and margin of error. Then there is simply real life intruding upon us. We might know the physical characteristics for a certain metal, but we are probably not taking into account things like crystal size, crystal boundry properties, and nuclear scale defects and doping. Then you have the simple fact that computers aren't instantaneous and all powerful. Modeling something like the rolling rubber band would be even harder than making a CGI movie out of it, and CGI movies can take many, many hours of render time. It can't be broken up, the number of calculations would be far greater than the number of pixels on a screen, so each frame/unit of time would have to be calculated in full before moving on to the next. When doing physics modeling, you can be dealing with a literally astronomical number of points (say when modeling the motion of a galaxy with 400 billion stars). Then you could be calculating that over an astronomical period of time. In the end, computers aren't all powerful and there are limits to how much can be modeled accurately.

Flying out of the drum by azmodean+1 · 2010-07-29 02:20 · Score: 3, Interesting

I was amused by this aside:

(The team couldn't study what happened when the two sides touched: The friction of the two sides moving in different directions sent the rubber bands flying out of the drum.)

What? It seems pretty obvious that they could see exactly what happened when the two sides touched, "The friction of the two sides moving in different directions sent the rubber bands flying out of the drum".

Re:Flying out of the drum by Anonymous Coward · 2010-07-29 04:02 · Score: 0

Yes, but the event in question happened too quickly for them to properly observe it, so they couldn't study it. They were studying the effects *within* the system that is the rubber band, not within the system that is the *room* containing the rubber band and drum.
Re:Flying out of the drum by Anonymous Coward · 2010-07-29 06:55 · Score: 0

Imagine the drum as a treadmill. You speed it up and start to trip over your own feet. You could still keep going in a weird tripping jog maybe. However you slow down a bit and the treadmill throws you off.
So the scientists can't study how you jog when you're tripping over your own feet because you're not on the treadmill anymore. It would be different if you were pushed off the top of a very tall and steep hill and couldn't stop.

Pulling it together by Anonymous Coward · 2010-07-29 02:26 · Score: 0

Ummm... how much of a stretch was it to write/fund the research/report?

Re:Isn't the center of a golf ball a rubberband ba by teebob21 · 2010-07-29 02:55 · Score: 1

This.

it is so tightly wound and then encased with little to no wiggle room that this alteration of shape would not take place.

--
khasim (12/9/06): In a blind taste test, more people preferred Coke over the Pepsi that I had previously pissed in.

In other news by hviniciusg · 2010-07-29 02:59 · Score: 1

"study reveals that the faster it goes, the more squashed it gets."

in other news, when it rains things get wet

BZZT! WRONG! by gbutler69 · 2010-07-29 03:05 · Score: 2, Interesting

You, like many of the others above, FAIL! There is Centrifugal Force. If I spin a rock at the end of a rope, the rock experiences a "Centripetal Force" which is a force pulling towards the center of a circle, where my hand is, that is perpendicular to it instantaneous velocity. Note, it is not only experiencing a "Centripetal Force", otherwise it would just accelerate along the radius toward the center. It is in fact also experiencing a force along the tangent (i.e. the diretion of instantaneous velocity) of the same circle. But, here is where it gets interesting. It is actually experiencing neither of those. It is in fact experiencing a force that is at an angle slightly between the direction of the tangent to the circle and along the radius. We can break that actual force (the real direction I'm actually pulling on the string) into the component along the radius and the component along the tangent, but, there really isn't two separate forces acting, just one. So, what you are calling "Centripetal Force" doesn't actually exist either. It's just a a convenient name for the component of the force pulling inward along the radius. Now, according to Newton's Laws, for every force (action) there is an equal an opposite force (re-action). So, if there is a corresponding force pulling inward on the rock (the "Centripetal Force") then there is also a force pulling outward along the radius (the "Centrifugal Force"). In fact, the Rock is pulling on my hand with such an equal and opposite force. So, my hand (and the string) is experiencing "Centrifugal Force". So, "Centrifugal Force DO EXIST!" You FAIL! Go back and re-read your Physics text-book and try again!

Thank You for Playing!

--
Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.

Re:BZZT! WRONG! by flaco629 · 2010-07-29 03:45 · Score: 1

You certainly are abrasive, for being so wrong. I read physics books every day, since I am a physicist.
Re:BZZT! WRONG! by clone53421 · 2010-07-29 03:52 · Score: 1

What you mean is, this is a REAL imaginary force that you invented to FIX Newton’s INCORRECT laws of motion so that they can apply to situations that they DON’T APPLY TO.
http://en.wikipedia.org/wiki/Newton's_laws_of_motion

Newton's Laws hold only with respect to a certain set of frames of reference called Newtonian or inertial reference frames.
Fail, indeed...

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:BZZT! WRONG! by flaco629 · 2010-07-29 04:00 · Score: 1

The observers are in an inertial frame of reference. The rubber band is a non-inertial frame of reference. So the experimenters cannot use a fictitious force in their bookkeeping to explain the motion of the rubber band.
Re:BZZT! WRONG! by gbutler69 · 2010-07-29 04:05 · Score: 1

OK, smart-ass physicist, which part of what I said is wrong?

--
Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.
Re:BZZT! WRONG! by gbutler69 · 2010-07-29 04:19 · Score: 1

Who said anything about rubber bands? The Parent said "There is no such thing as Centrifugal Force". I explained, and clearly showed, how there is such a thing as Centrifugal Force. If you are going to call me wrong, address what I said.

--
Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.
Re:BZZT! WRONG! by clone53421 · 2010-07-29 04:39 · Score: 1

Centrifugal forces don't exist. They are fictional forces used to make non-inertial frames of reference conform to Newton's laws.
You want me to address what you said? Fine. Here goes.

Note, it is not only experiencing a "Centripetal Force", otherwise it would just accelerate along the radius toward the center.
BZZT! WRONG! It IS only experiencing a centripetal force, and it IS just accelerating along the radius toward the center. You just THINK it isn’t. It’s called momentum.

But, here is where it gets interesting. It is actually experiencing neither of those. It is in fact experiencing a force that is at an angle slightly between the direction of the tangent to the circle and along the radius.
BZZT! WRONG! A string can only transmit a linear tensile force parallel to itself. It is IMPOSSIBLE for a string to transmit a force such as that which you just described.

So, what you are calling "Centripetal Force" doesn't actually exist either. It's just a a convenient name for the component of the force pulling inward along the radius.
BZZT! WRONG! Forces aren’t some sort of imaginary vectors. They are REAL FORCES applied by PHYSICAL THINGS. If there is no physical thing to cause a force, you cannot have a force. The only force that does not require a physical thing actually IN CONTACT with the object is, of course, gravity. A string can transfer a tensile force parallel to itself. No other sort of force. Any sideways force applied to a string will just skew it, and any compressive force will merely collapse it.

Now, according to Newton's Laws, for every force (action) there is an equal an opposite force (re-action).
BZZT! WRONG! – no, YOU aren’t wrong, Newton’s laws are! Newton’s laws do NOT apply to accelerating frames of reference, and you are wrong for trying to apply them to one.

In fact, the Rock is pulling on my hand with such an equal and opposite force.
BZZT! WRONG! The rock is not pulling your hand, it is merely trying to remain in its inertial state. You are trying to change its inertial state – accelerate it – and it resists this.

You FAIL! Go back and re-read your Physics text-book and try again!
Thank You for Playing!
Here’s a suggestion: why don’t YOU go take some college-level physics and actually try to UNDERSTAND some of this stuff that you think you know so much about?
I’ve taken both college-level physics and calculus and I know that if you integrate a constant force parallel to the string – centripetal force – AND NO OTHER FORCES, then you take a specific initial velocity at a certain tangential velocity perpendicular to the force – you get the velocity vector of a circularly orbiting object traveling at a constant speed but with constantly changing direction. NO OTHER FORCE EXISTS IN THE SYSTEM, AND THE CALCULUS SUPPORTS THIS.

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:BZZT! WRONG! by flaco629 · 2010-07-29 04:49 · Score: 1

"It is in fact also experiencing a force along the tangent (i.e. the diretion of instantaneous velocity) of the same circle. But, here is where it gets interesting. It is actually experiencing neither of those. It is in fact experiencing a force that is at an angle slightly between the direction of the tangent to the circle and along the radius." The only force it experiences is radial. There is no tangental component of force. There is a tangential velocity at all times, but the magnitude of that velocity never changes, only the direction, because no work is done - work is given by the integral of the dot product of force and displacement , which are at all time perpendicular to each other, so the dot product is zero. No work is done. Thus no tangential component of force. "So, if there is a corresponding force pulling inward on the rock (the "Centripetal Force") then there is also a force pulling outward along the radius (the "Centrifugal Force"). In fact, the Rock is pulling on my hand with such an equal and opposite force. So, my hand (and the string) is experiencing "Centrifugal Force". So, "Centrifugal Force DO EXIST!" " The rock is exerting a reaction force on your hand. But this on no way implies that there is an outward force on the rock. Action and reaction forces are exerted on DIFFERENT bodies. The force on the rock is unbalanced, That is why the velocity of the rock changes direction. You seem to the think the centrifugal force is exerted on your hand. Getting back to the rubber band in TFA, what does it exert centrifugal force force on? There is no hand. And you are abusing an already misused term. Centrifugal force, if it were real, would be exerted on the rock, not the string or your hand.
Re:BZZT! WRONG! by gbutler69 · 2010-07-29 04:52 · Score: 1

Here is where your analysis is incomplete and WRONG! What gives the rock it's momentum along the tangent? The String. Which is NOT pulling straight towards the center of the overall circular motion. In order for me to make the thing start swinging I need a big pull initially NOT in the direction of the center that I'm going to revolve the rock around. Then, also, I need to continue to impart a slight force along the tangent in order to overcome air resistance. Therefore, I am not consistently pulling directly towards the center of the overall motion. Then you say, the rock is not pulling back on my hand with an equal force to the centripetal force that it is experiencing. You say, what I feel is the inertia of the rock. Yeah, that inertia is imparting a force onto the string and my hand. That force is directed outward radially. It is a centripetal force. Yes, I have calculated this using Calculus as well. Yes, I know there is not CENTRIFUGAL FORCE acting on the ROCK, but, there is a CENTRIPETAL FORCE acting on my hand and the string that IS a manifestation of the intertia of the rock. I think that perhaps you understand less than you think you do.

--
Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.
Re:BZZT! WRONG! by gbutler69 · 2010-07-29 04:55 · Score: 2

That force is directed outward radially. It is a centripetal^h^h^h^h^h^h^h^h^h^h^hCENTRIFUGAL force. Yes, I have calculated this using Calculus as well. Yes, I know there is not CENTRIFUGAL FORCE acting on the ROCK, but, there is a CENTRIPETAL^h^h^h^h^h^h^h^h^h^h^hCENTRIFUGAL FORCE acting on my hand and the string that IS a manifestation of the intertia of the rock.
Woops! In my haste I had a couple of typos.

--
Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.
Re:BZZT! WRONG! by flaco629 · 2010-07-29 05:02 · Score: 1

Wrong again. Inertia gives it momentum along the tangent. I do not have time to refute every mistake you make because there are so many. Likewise, think that perhaps you understand less than you think you do. Either that, or you are a troll.
Re:BZZT! WRONG! by gbutler69 · 2010-07-29 05:09 · Score: 1

The rock is exerting a reaction force on your hand.
Yes, that is what I said

But this on no way implies that there is an outward force on the rock
Errm, when did I say there was?

Getting back to the rubber band in TFA, what does it exert centrifugal force force on?

What does that have to do with anything? You said, "Centrifugal Forces do not exist", not "Centrifugal Forces are not applicable to the current problem."

Centrifugal force, if it were real, would be exerted on the rock, not the string or your hand.
What an odd definitiaon of "Real"?!?!

You seem to the think the centrifugal force is exerted on your hand.
Yeah, it is! And to point out your earlier quote...

The rock is exerting a reaction force on your hand.
Yep, just what I said. So, we're in agreement that the rock exerts a centrifugal force on my hand, but, then you question me when I think that. Hmmm, it seems to me that you are forgetting the basics and getting wrapped up in the wrong details and the wrong way of looking at it
In your other post you finish with:

I’ve taken both college-level physics and calculus and I know that if you integrate a constant force parallel to the string – centripetal force – AND NO OTHER FORCES, then you take a specific initial velocity at a certain tangential velocity perpendicular to the force – you get the velocity vector of a circularly orbiting object traveling at a constant speed but with constantly changing direction. NO OTHER FORCE EXISTS IN THE SYSTEM, AND THE CALCULUS SUPPORTS THIS.
Well, let's have a look at this. Force Parallel to String - Check. Constant Velocity of Rock - Check. Changing Velocity - Check. Then you say, "NO OTHER FORCE EXISTS IN THE SYSTEM". WHAT? What are you considering "THE SYSTEM"? All you talked about was the forces acting on the rock, nothing else. "THE SYSTEM" is my hand, the string, and the rock. Now, what are all the FORCES? What's that tug I feel on my hand that I have to exert energy to overcome? Oh, that's the CENTRIFUGAL FORCE my hand is experiencing.

--
Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.
Re:BZZT! WRONG! by clone53421 · 2010-07-29 05:10 · Score: 1

What gives the rock it's momentum along the tangent? The String.
That is so wrong it’s not even funny any more. Momentum is a property of mass. Any mass that is moving has momentum. It has NOTHING TO DO WITH THE STRING. If the string vanished, the rock’s momentum would carry it in a perfectly straight line along its tangent. The string is only there to supply a force PERPENDICULAR to its line of motion. This is the ONLY force in action on the object.
http://en.wikipedia.org/wiki/Momentum

In classical mechanics, momentum (pl. momenta; SI unit kgm/s, or, equivalently, Ns) is the product of the mass and velocity of an object (p = mv).
We’re done here. You can ask ANY college physics professor and he will tell you the exact same thing I have been telling you. Your claim that you have “calculated this using Calculus” is ludicrous; if you try calculate it with ANY OTHER FORCES besides centripetal force, IT DOESN’T WORK. The only force in the equation is the centripetal force. Not to mention that you don’t have any way of APPLYING your imaginary forces to the object. A string can only pull.

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:BZZT! WRONG! by gbutler69 · 2010-07-29 05:23 · Score: 0, Troll

OK, so where is the force coming from to overcome air resistance to keep imparting a tangential component to the velocity? The rock has an instantaneous velocity tangent to the circle. That means it will experience an opposing force in the opposite direction also tangent to the circle that will slow the velocity causing it to lose momentum and stop. Now, what is overcoming this air resistance? Well, I'm pulling the string slightly (ever so) ahead of a line perfectly perpendicular from the objects instantaneous velocity and the center of the circle about which I am causing it to revolve. So, no, I am not wrong. You are over-simplifying and ignoring the obvious. YOU ARE WRONG! You call me wrong and fail to point out why. You are an arrogant asshole that gives scientists and mathematicians a bad name. You are the reason why people tend not to believe proper scientists, engineers, and mathematicians. You are so certain you are right because you are so EDUMACATED that you fail to see the obvious flaws in your reasoning.

--
Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.
Re:BZZT! WRONG! by clone53421 · 2010-07-29 05:27 · Score: 1

In a frictionless environment, the centripetal force need only be enough to accelerate the velocity vector while remaining at the same absolute value (same speed but a slightly different direction).
Now, since you want to take friction into account, the centripetal force needs to be slightly larger (than in the frictionless system) so as to accelerate the velocity vector so that, combined with the effect of the friction, the velocity vector still is accelerated so as to result in the same speed at a slightly different direction.

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:BZZT! WRONG! by flaco629 · 2010-07-29 05:33 · Score: 1

You are such an ignorant dolt you fail the see the glaring flaws in your own reasoning. You have at least two people pointing out your obvious mistakes in this thread. Instead of trying to understand why your logic is flawed, you resort to base profanity. Most impressive.
Re:BZZT! WRONG! by XSpud · 2010-07-29 09:47 · Score: 1

Now, what are all the FORCES? What's that tug I feel on my hand that I have to exert energy to overcome? Oh, that's the CENTRIFUGAL FORCE my hand is experiencing.
Perhaps I'm going off the original point of the discussion a bit, but since this is all about understanding physics I thought I should point out that you do not need to exert energy to "overcome" a force. It's only if that force does work that energy is expended. Replace your hand with a rigid post and it will still experience a force, though it clearly doesn't expend energy.
Re:BZZT! WRONG! by Anonymous Coward · 2010-07-29 10:19 · Score: 0

It's only if that force does work that energy is expended.
I don't think you are right. If I stand and push against an effectively immovable wall for an hour as hard as I can I will not have done any work (W = FxD) but, I have surely expended energy. I will have surely burned a lot of calories.
Re:BZZT! WRONG! by Anonymous Coward · 2010-07-29 11:02 · Score: 0

In clarification, don't confuse work with energy. They aren't quite exactly the same thing. What is correct to say, is a force does no work if it does not cause a displacement of the object along the vector of the force. This says nothing about the expense of energy though other than to say, an appropriate amount of energy expended will accounted for in the work done. It does not mean that that is the only energy expense nor that for energy to be expended work must be done.
Re:BZZT! WRONG! by XSpud · 2010-07-29 11:38 · Score: 2, Informative

Yes you will have burned calories but you will have done no work on the wall. The work performed will have been within your body caused by the contraction of muscles. The energy expended will have been converted to heat, presumably now lost to the environment through your skin if you're still alive ;-)
If you want to consider all forces and energy transfers within a human body when pushing against a wall, there's a lot to consider - it's far simpler to assume the body is rigid and has no internal structure that you need to be concerned about - in your example perhaps think of a rigid body leaning against a wall, which will impart a force but does not expend energy. In this case we would only need to consider mechanical properties of the system rather than the thermodynamic properties that apply to all real-world systems.
Of course if you are a biologist it might be valid to look at the the energy expended pushing against a stationary wall for an hour. In this case they might want to consider the the source of the energy (chemical), how forces act on the skeleton, the mass of limbs etc - not very useful though if you want to understand fundamental concepts of physics.
Reading through the discussion above and below, it's clear that posters are talking about different systems - this is why the first thing an applied mathematician or physicist does is to draw a diagram, and to state any assumptions. For example I think gbutler69 was talking about a system with the "hand" moving in a circle to impart a force to maintain the kinetic energy of the rock, where KE was being lost to air friction, and the responders were assuming a frictionless system with a rigid, fixed "hand".
To prevent a similar flamewar I should mention that in my example above, the rigid post is attached to the ground, which is also rigid and has infinite mass ;-)
Re:BZZT! WRONG! by gbutler69 · 2010-07-29 12:20 · Score: 1

Reading through the discussion above and below, it's clear that posters are talking about different systems - this is why the first thing an applied mathematician or physicist does is to draw a diagram, and to state any assumptions. For example I think gbutler69 was talking about a system with the "hand" moving in a circle to impart a force to maintain the kinetic energy of the rock, where KE was being lost to air friction, and the responders were assuming a frictionless system with a rigid, fixed "hand".
Yes, that is what I've been saying all along. They keep wanting to talk about the system as the ROCK and what forces are acting on it in its non-inertial frame of reference. Or they want to talk only about the forces acting on the rock in the inertial frame of reference. I was talking about the forces acting within the system of hand, string, rock. Where there is clearly a notion of Centrifugal Force that agrees with all accepted definitions of the term and is commonly used in engineering calculations etc when determining internal stresses of a system. Thank You kindly for bringing further clarification to the point.

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Re:BZZT! WRONG! by XSpud · 2010-07-29 13:32 · Score: 1

In clarification, don't confuse work with energy. They aren't quite exactly the same thing. What is correct to say, is a force does no work if it does not cause a displacement of the object along the vector of the force. This says nothing about the expense of energy though other than to say, an appropriate amount of energy expended will accounted for in the work done. It does not mean that that is the only energy expense nor that for energy to be expended work must be done.
It's a long time since I was really up on physics and maths and I may have been imprecise with terminology etc. I agree that the vector components of the force need to be considered - particularly important for the string-rock system under discussion where the force on the rock along the tangent is 0, hence the KE does not change (assuming string is attached to a fixed point, frictionless system etc). I'm not sure I understand your last sentence - are you thinking about systems with friction etc?
I've enjoyed reading these posts - it's good to get back up to speed with some of the basic concepts I used to be familiar with as a student. I've found a couple of the links here useful.
Re:BZZT! WRONG! by clone53421 · 2010-07-30 01:37 · Score: 1

No, the AC’s last sentence is not referring to friction.

It does not mean that [the energy that does do work] is the only energy expense nor that for energy to be expended work must be done.
Essentially, it means this: To do work, one must expend energy. However, expending energy does not necessarily do work; a fraction of the energy you expend may accomplish no work and in fact it is possible to expend energy and not do any work.
For instance, holding a brick out stationary at an arm’s length requires a good deal of energy (effort) but accomplishes no work in the physics sense (because it is stationary).
Work is the dot product of force and displacement. If you recall the definition of the dot product of two vectors, it is the product of their magnitudes multiplied by the cosine of the angle between them. In other words, if they are parallel vectors the magnitude of the dot product is at its maximum value (the product of the magnitudes of the original two vectors) while if they are at 90 degree angles (perpendicular) to each other their dot product is zero and no work is being done by the force.

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.

Oh, one other thing... by gbutler69 · 2010-07-29 03:11 · Score: 1

Every Molecule in the Rock and String, other than the single Molecule that is farthest from the center of the circle, simultaneously feels a Centripetal, and Centrifugal Force. That is because that while each molecule is experiencing a force pulling towards the center of the circle, that same molecule is also pulling on the next molecule in the chain, which is pulling back, therefore the first molecule experiences a "Centrifugal Force" equal to the "Centripetal Force" it pulls with to the next molecule in the chain. So, one can say everything in the system other than the outermost molecule is experiencing "Centrifugal Force". Now, is it so incorrect to talk about "Centrifugal Force"? Me thinks not. It is simpler to think of the system in terms of "Centripetal Force" and "Radial Force", but, you can also think of it in terms of "Centrifugal Force" quite well.

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Re:Oh, one other thing... by clone53421 · 2010-07-29 05:22 · Score: 1

No, every molecule has a velocity and momentum and a centripetal force perpendicular to its direction of travel which accelerates it into a new velocity at the same absolute speed but at a slightly different direction such that its distance from the middle of the circle remains constant. There is no centrifugal force acting on the molecule. It’s imaginary. It does not exist.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:Oh, one other thing... by gbutler69 · 2010-07-29 05:39 · Score: 1

My hand is hold a string. String is glued to surface or rock. I begin spinning it. The string is exerting a centripetal force on the rock via the molecules on the inward surface of the rock. These molecules are pulling inward on the next layer of molecules. The first layer of molecules are feeling a force outward (CENTRIFUGUAL FORCE) that equals the force they are pulling the other molecules inward with. This outward force that the first layer of molecules feels is exactly equal to the force required to impart the necessary inward accelleration to all of the outward mass for it to follow a circular path. The inward force on the inward layer of molecules is greater than the outward pull of the remainder of the pass so the inward layer of molecules feel a net inward force. So, yes, in all cases the NET force is only inward, but, the individual components are not only inward.

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Re:Oh, one other thing... by clone53421 · 2010-07-29 05:41 · Score: 1

But there is no centrifugal force. You are talking about momentum. Momentum is inertia. It is not a force. Newton was wrong; his laws of motion do not apply to changing inertial frames of reference.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.

Indeed by stomv · 2010-07-29 03:34 · Score: 1

but I'm surprised that they didn't get a bigger drum, in order to minimize the curvature of the surface with which the elastic was in contact. I have no idea if their model corrects for the fact that the elastic is not rolling down a 'flat' surface, but rather one with a curve. Bigger drum, smaller curve.

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Re:Indeed by JWSmythe · 2010-07-29 10:15 · Score: 1

They could have avoided the curve entirely by using a belt. Think like a conveyor belt. A variable speed belt sander on an incline would have probably achieved exactly what they needed. It would have been better to make a custom rig with three spindles and a wide belt. One spindle would be attached to a variable speed motor. The second spindle would just be a second fixed point. The third spindle would be a tensioner to ensure your flat moving surface is still flat.
Physicists shouldn't do tasks best left up to engineers.

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Serious? Seriousness is well above my pay grade.

Seems to be remembering the curvature of the drum by spads · 2010-07-29 03:40 · Score: 1

The idea is that as they speed it up, it doesnt have time to "relax" from its curvature from conforming to the drum. They should try it with larger diameter drums.

So called "visco-elastic" materials (e.g. polymers) are extremely interesting. Basically, you can clearly see the (mechanical) molecular properties manifesting themselves at the mechanically at the macroscopic scale. If I am write about this one, that would be mainly due to the viscosity.

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Bukowski said it. I believe it. That settles it.

Reminds me of a Feynman story by Anonymous Coward · 2010-07-29 04:41 · Score: 0

That kind of reminds me of a Feynman story. At one point, I think in the 1950's, he was kind of in a funk and not really into physics at all. Then one day he watched a plate thrown into the air spinning and wobblingand was fascinated. He spent some time working out the physics of the spinning plate and kind of got interested in physics again. He jumped back into physics and started working on quantum electrodynamics for while he was later awarded the Nobel Prize. Ironically, the physics he worked out for the spinning plate had an application for an electron spinning as well and was used in his QED work.

Wow! More false statements by you... by gbutler69 · 2010-07-29 05:27 · Score: 1

The only force that does not require a physical thing actually IN CONTACT with the object is, of course, gravity.

Hmmm, well, the Electo-Magnetic, Strong, and Weak Nuclear forces would beg to differ with you

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Re:Wow! More false statements by you... by clone53421 · 2010-07-29 05:39 · Score: 1

The strong and weak nuclear forces DO require physical contact, unless you’re talking about separation distances in the femtometer range.
You’re clearly an asshat.

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.

Galileo Or Newton by Anonymous Coward · 2010-07-29 05:47 · Score: 0

Newton may have given credit to Galileo for his first law but the principles being employed for motion and acceleration here have more to do with Newton's work than Galileo, I'd suspect.

OK... by gbutler69 · 2010-07-29 05:52 · Score: 1

I'm an asshat because, "strong and weak nuclear forces DO require physical contact, UNLESS YOU'RE TALKING ABOUT SEPARATION DISTANCES IN THE FEMTOMETER RANGE". So, first we are talking about separation and not physical contact for these forces to act on the scales that they normally are applicable. But, then you completely ignore the HUGE PINK ELEPHANT in the room, "Electro-Magnetic" which have effects over very large distances. So, yeah, I guess I'm an asshat for pointing out that gravity is not even close to the only force that doesn't require contact to have an effect. Yeah, I'M THE ASSHAT! RIGHT!

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Re:OK... by clone53421 · 2010-07-29 07:41 · Score: 1

Yes, you are an asshat. The physical contact between your fingers and the keyboard on which you are typing this retarded shit is on the order of femtometers. ALL physical contact is on the order of femtometers at the least, unless we are talking about an atom-smasher that actually tries to get two bits of matter to touch just to see what sort of fireworks that causes.
I wrote something about the electromagnetic forces but apparently my quote tags got screwed up and Slashcode ate it. I must have left out a closing angle bracket. Something to the effect of we weren’t talking about electromagnetism at all, hence I forgot to include it, and if we are talking about it then we have a completely different system than one in which we are just considering centripetal forces – and I only threw in gravitation because it would almost always apply to any system we’d be considering even if we chose to ignore it for simplicity.
Anyway, the fact of the matter is you are wrong – ludicrously so – all along and at least two people who clearly know more about this than you have forgotten have both told you that you’re utterly dead wrong and now you’re just finding pedantic asshat excuses to quibble over a force that I omitted when I said that forces need physical objects in order to be transmitted.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.

No, you are the ignorant dolt. by gbutler69 · 2010-07-29 05:59 · Score: 1

What is that force my hand feels pullling on it? Which direction does it point? Answer: Away from the center of the circle about which the rock is revolving. So, is is CENTRIFUGAL (i.e. a force pointing away from the center) FORCE exerted against my hand. How can you not see this? You keep saying, "There is no centrifgual force on the rock". Yep, I agree. But, to deny that there is a CENTRIFUGAL FORCE on my hand is ludicrous!

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Why you are an asshole. by gbutler69 · 2010-07-29 06:01 · Score: 1

You are an asshole because you keep pointing out how I'm wrong that the rock is experiencing CENTRIFUGAL FORCE when I never made any such claim. I said, very clearly, that my hand and the string was experiencing a CENTRIFUGAL FORCE. You cannot deny this is true without sounding like an asshole to me. And as far as profanity is concerned, I consider it completely acceptable to call an asshole an asshole. So bite me!

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Re:Why you are an asshole. by flaco629 · 2010-07-29 06:23 · Score: 1

Ok, internet tough guy. Real scary. I will make this simple enough for you to understand. If you cut the string, the rock will fly off in a straight line along its' instantaneous velocity due to its inertia. It is sometimes mistakenly attributed to centrifugal force, which does not exist. You are the first person I know of who believed centrifugal was exerted on the hand or the string. Thank you for elucidating this for us. I'm sure Stockholm will soon be calling to award you for your great insight, which had escaped Newton, Einstein, Feynman, and all the rest. You have truly joined the ranks of the the all-time greats of physics. Or rather should I say you are a simpleton and a blowhard.
Re:Why you are an asshole. by gbutler69 · 2010-07-29 06:34 · Score: 1

Replace a part of the string with a spring. Now, cut the string between the string and the rock. The rock flies off tangent to the circle, obviously no centrifugal force on the rock. The spring instantaneously springs back. What was pulling outward on the spring? A centrifugal force! Duh! Yeah, I'm a blow-hard and a simpleton. I think not. You foolishly argued with me about there not being a centrifugal force on the rock when I never said there was. I said, over, and over, and over, and over again I was talking about the force exterted outward on the string or on my hand. You are repeating something you KNOW to be sure without truly thinking or listening to the other person. In summary, YOU ARE AN ASSHOLE!

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Re:Why you are an asshole. by flaco629 · 2010-07-29 06:50 · Score: 1

Take it slow and read so you can understand every word. The term "centrifugal force", as used by the entire world, refers to the rock, not your hand. We are talking apples, you are talking oranges. Your whole argument is pointless because you are misusing the term. The parent of the thread was talking about a centrifugal force on a rubber band rolling down a slope. We informed him the term was a misnomer. You piped in with some nonsense about centrifugal force being a reaction a rock exerts on a string. And you have repeatedly made a fool of yourself trying to defend an untenable position.

must be done in a vacuum by Anonymous Coward · 2010-07-29 06:23 · Score: 0

inside the loop the top and the bottom of the loop are moving in opposite directions causes an increase in apparent wind direction at the mid-point between the loops causing a low atmospheric pressure point forcing the bands together. perform this experiment in a vacuum and the rubber band should become circular

wtf? by gbutler69 · 2010-07-29 07:00 · Score: 1

The WHOLE WORLD used centrifugal force to refer to the rock even though it doesn't exist? What the hell are you talking about? The ONLY context I've ever heard centrifugal force be rightly used is when applied to the rock and the string (i.e. the thing exerting the centripetal force). This is basic. I was only responding to the contention that "there is no such thing as Centrifugal Force". Yes there is. Centripetal Force (center seeking) means a force directed towards the center of a circle. It means that you are defining a force vector that is constantly changing in direction with respect to time so as to always point towards the center of a circle. Centrifugal Force is the opposite. It is a force that is dynamically changing in direction with respect to time such that it always points outward from the center of a circle. Centripetal vs. Centrifugal are just words to describe the dynamically changing direction of a particular force in a system. When looking at the hand, string, rock system as described, my hand and the string both experience a Centrifugal Force (put a spring in there and prove it). The rock is experiencing a centripetal force. What is so fucking hard for you to grasp? You are an ASSHAT!

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Re:wtf? by gbutler69 · 2010-07-29 07:02 · Score: 1

used is when applied to the rock and the string
Correction: I meant, "...when applied to the HAND and the string..."

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Re:wtf? by flaco629 · 2010-07-29 07:17 · Score: 1

Does it make you feel like a hard man to swear at people online? You are using terms contrary to conventional usage, so that your arguments are simply meaningless. Above you write "The ONLY context I've ever heard centrifugal force be rightly used is when applied to the rock and the string" but earlier your "proof" of the existence of the centrifugal force was that the rock exerted a reaction force on the hand. So which is it? Does the centrifugal force apply to the rock or the hand?
Re:wtf? by gbutler69 · 2010-07-29 07:19 · Score: 1

Did you read my correction that I made immediately after posting? I already corrected myself.

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Re:wtf? by flaco629 · 2010-07-29 07:25 · Score: 1

As I patiently explained at a simple enough level for even you, that is not how the term is used. In the parent of the thread, even if the rubber band were exerting a "centrifugal force" ( on what? There is no hand or anything else for it to exert that force on), how would it affect the motion of the rubber band itself? You started your bizarre arguments in response to my saying there was no such force acting on rubber band, don't reply "Who said anything about rubber bands" as you did above.
Re:wtf? by Anonymous Coward · 2010-07-29 07:27 · Score: 0

Does it make you feel like a hard man to swear at people online?
Nope, words are words. Nothing special about "swear" words (your term). Does it make you feel superior to call people dolts etc. when you obviously haven't read what they said. I think you are full of shit. No the whole world does not consider "Centrifugal Force" to refer to the rock. Any proper usage of that word or course refers to the string or the hand (or the inserted spring if that makes it more clear). That is what I was pointing out. You arguing with me shows that your "understanding" is just repetition of some formulas and concepts you learned without real though about the matter.
Re:wtf? by flaco629 · 2010-07-29 07:31 · Score: 1

You didn't correct yourself. You repeated your previous error.
Re:wtf? by Anonymous Coward · 2010-07-29 07:35 · Score: 0

You did not say, "there is no applicable centrifugal force in this rubber-band system", you said, "there is no such thing as centrifugal force". I explained how there is something rightly called "centrifugal force" and what that force is in the context of the classical example of "centripetal force" that people wrongly call "centrifugal force". In other words, I was trying to clarify the difference between "centrifugal" and "centripetal" force for those who might not understand and would be mislead by the claim that "centrifugal force does not exist". You were immediately dismissing and insulting. I called you out. You're an asshole and you're obviously not a very good physicist (if you even are one). So, nah-na-nah-na boo-boo stick your head in doo-doo!
Re:wtf? by clone53421 · 2010-07-29 07:51 · Score: 1

What you keep calling “centrifugal force” is INERTIA. Stop calling it centrifugal force. It isn’t.

--
Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:wtf? by Anonymous Coward · 2010-07-29 07:51 · Score: 0

A reactive centrifugal force is the reaction force to a centripetal force. A mass undergoing curved motion, such as circular motion, constantly accelerates toward the axis of rotation. This centripetal acceleration is provided by a centripetal force, which is exerted on the mass by some other object. In accordance with Newton's Third Law of Motion, the mass exerts an equal and opposite force on the object. This is the reactive centrifugal force. it is directed away from the center of rotation, and is exerted by the rotating mass on the object that originates the centripetal acceleration.[10][11][12]
This conception of centrifugal force is very different from the fictitious force (i.e. the centrifugal force of common experience). As they both are given the same name, they may be easily conflated. Whereas the 'fictitious force' acts on the body moving in a circular path, the 'reactive force' is exerted by the body moving in a circular path onto some other object. The former is useful in analyzing the motion of the body in a rotating reference frame. The latter is not.
The concept of the reactive centrifugal force is used often in mechanical engineering sources that deal with internal stresses in rotating solid bodies.[13] Newton's reactive centrifugal force still appears in some sources, and is often referred to as just centrifugal force rather than as reactive centrifugal force.[14][15][16][17][18][19][20][21][22]
Re:wtf? by clone53421 · 2010-07-29 07:59 · Score: 1

IT IS NOT!
Look, here’s a simple example of EXACTLY the same phenomenon that maybe even a moron like you will be able to comprehend.
You have a refrigerator on the back of your truck. Since you are a moron, you have it upright and don’t have it tied down at all. When you pull out of the parking space, lo and behold the refrigerator falls flat on its side and slides off the end of your truck bed.
Conclusion: Centrifugal force PUSHED that refrigerator over and right off the back of your truck. Refrigerators don’t just fall over! They have to be PUSHED. Oh yes indeed, it’s all the fault of that damn centrifugal force...
This is EXACTLY the same. The only difference is that it is a linearly accelerating frame of reference instead of a circularly accelerating one.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:wtf? by gbutler69 · 2010-07-29 08:06 · Score: 1

Wow! You really are a complete piece of shit! You have repeatedly called me stupid and names while refuting something I never claimed. You are a fool. You don't understand what the fuck you are talking about. Fuck you you lousy, rotten, stupid jack-ass.

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Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.
Re:wtf? by gbutler69 · 2010-07-29 08:07 · Score: 1

A reactive centrifugal force is the reaction force to a centripetal force. A mass undergoing curved motion, such as circular motion, constantly accelerates toward the axis of rotation. This centripetal acceleration is provided by a centripetal force, which is exerted on the mass by some other object. In accordance with Newton's Third Law of Motion, the mass exerts an equal and opposite force on the object. This is the reactive centrifugal force. it is directed away from the center of rotation, and is exerted by the rotating mass on the object that originates the centripetal acceleration.[10][11][12] This conception of centrifugal force is very different from the fictitious force (i.e. the centrifugal force of common experience). As they both are given the same name, they may be easily conflated. Whereas the 'fictitious force' acts on the body moving in a circular path, the 'reactive force' is exerted by the body moving in a circular path onto some other object. The former is useful in analyzing the motion of the body in a rotating reference frame. The latter is not. The concept of the reactive centrifugal force is used often in mechanical engineering sources that deal with internal stresses in rotating solid bodies.[13] Newton's reactive centrifugal force still appears in some sources, and is often referred to as just centrifugal force rather than as reactive centrifugal force.

--
Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.
Re:wtf? by clone53421 · 2010-07-29 08:10 · Score: 1

You’re the one who can’t write a post without a stream of profanities throughout.
You claimed that there is a real force which you call centrifugal force. This has been refuted by multiple people multiple times in every way conceivable. There is no such thing as centrifugal force. It is merely inertia, and Newton’s laws of motion do not apply because the frame of reference is accelerating. That you are too dumb to realise that you’re completely wrong, to dumb to realise that you have even been refuted, and in any case too dumb to quit arguing, I have concluded that stupid is a pretty good adjective to describe you.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:wtf? by gbutler69 · 2010-07-29 08:10 · Score: 1

No, what you keep claiming that I am calling Centrifugal Force is inertia. What I am calling Centrifugal Force is Centrifugal Force. From Wikipedia:

A reactive centrifugal force is the reaction force to a centripetal force. A mass undergoing curved motion, such as circular motion, constantly accelerates toward the axis of rotation. This centripetal acceleration is provided by a centripetal force, which is exerted on the mass by some other object. In accordance with Newton's Third Law of Motion, the mass exerts an equal and opposite force on the object. This is the reactive centrifugal force. it is directed away from the center of rotation, and is exerted by the rotating mass on the object that originates the centripetal acceleration.[10][11][12] This conception of centrifugal force is very different from the fictitious force (i.e. the centrifugal force of common experience). As they both are given the same name, they may be easily conflated. Whereas the 'fictitious force' acts on the body moving in a circular path, the 'reactive force' is exerted by the body moving in a circular path onto some other object. The former is useful in analyzing the motion of the body in a rotating reference frame. The latter is not. The concept of the reactive centrifugal force is used often in mechanical engineering sources that deal with internal stresses in rotating solid bodies.[13] Newton's reactive centrifugal force still appears in some sources, and is often referred to as just centrifugal force rather than as reactive centrifugal force.

--
Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.
Re:wtf? by clone53421 · 2010-07-29 08:11 · Score: 1

Quit trying to apply Newton’s third law to a situation to which it does not and cannot be applied. It causes such nonsense as needing imaginary forces to make your equations balance out.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:wtf? by clone53421 · 2010-07-29 08:18 · Score: 1

A reactive centrifugal force is the reaction force to a centripetal force. A mass undergoing curved motion, such as circular motion, constantly accelerates toward the axis of rotation. This centripetal acceleration is provided by a centripetal force, which is exerted on the mass by some other object. In accordance with Newton's Third Law of Motion, the mass exerts an equal and opposite force on the object. This is the reactive centrifugal force. it is directed away from the center of rotation, and is exerted by the rotating mass on the object that originates the centripetal acceleration.[10][11][12] This conception of centrifugal force is very different from the fictitious force (i.e. the centrifugal force of common experience). As they both are given the same name, they may be easily conflated. Whereas the 'fictitious force' acts on the body moving in a circular path, the 'reactive force' is exerted by the body moving in a circular path onto some other object. The former is useful in analyzing the motion of the body in a rotating reference frame. The latter is not. The concept of the reactive centrifugal force is used often in mechanical engineering sources that deal with internal stresses in rotating solid bodies.[13] Newton's reactive centrifugal force still appears in some sources, and is often referred to as just centrifugal force rather than as reactive centrifugal force.
That is inertia. It is not some special force that you can call centrifugal force. It is just inertia, and the fact that you or anyone else wants to call it a reactive centrifugal force does not make it anything other than inertia.
Pull on an object and its inertia pulls back. That is all.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:wtf? by clone53421 · 2010-07-29 08:19 · Score: 1

That is inertia. You are pulling an object and causing it to accelerate. Its inertia resists this.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
Re:wtf? by Anonymous Coward · 2010-07-29 08:33 · Score: 0

No, I am not wrong. There is a clearly recognized concept of Centrifugal Force that is the reactive force exerted on the body that is exerting the centripetal force on a revolving body. It is a widely used concept in Physics and Engineering and cannot be overlooked when dealing with the internal stresses of a system. You keep wanting the system to be the rock, when the system is my hand, the string, and the rock. When we talk about this system, there is a force that is clearly correctly referred to as Centrifugal Force. It doesn't act on the rock, like most people tend to think. The rock also experiences a FICTITIOUS force within it's own frame of reference traveling along a curved path that is also referred to as CENTRIFUGAL FORCE. These two are not the same thing. You want to call everyone stupid. You want to say the "Whole world means this when it says CENTRIFUGAL FORCE". And, when I provide a citation that shows that, no, there is in fact wide-spread recognition of the concept of CENTRIFUGAL FORCE you ignore it. You are a jerk-off. You probably sleep with your mother and molest children as much a cock-biter as you are. To quote:

A reactive centrifugal force is the reaction force to a centripetal force. A mass undergoing curved motion, such as circular motion, constantly accelerates toward the axis of rotation. This centripetal acceleration is provided by a centripetal force, which is exerted on the mass by some other object. In accordance with Newton's Third Law of Motion, the mass exerts an equal and opposite force on the object. This is the reactive centrifugal force. it is directed away from the center of rotation, and is exerted by the rotating mass on the object that originates the centripetal acceleration.[10][11][12]
This conception of centrifugal force is very different from the fictitious force (i.e. the centrifugal force of common experience). As they both are given the same name, they may be easily conflated. Whereas the 'fictitious force' acts on the body moving in a circular path, the 'reactive force' is exerted by the body moving in a circular path onto some other object. The former is useful in analyzing the motion of the body in a rotating reference frame. The latter is not.
The concept of the reactive centrifugal force is used often in mechanical engineering sources that deal with internal stresses in rotating solid bodies.[13] Newton's reactive centrifugal force still appears in some sources, and is often referred to as just centrifugal force rather than as reactive centrifugal force.
Re:wtf? by Anonymous Coward · 2010-07-29 08:39 · Score: 0

Hey asshat, check those parent links. You replied to your own post.
So, you just accused yourself of being a jerk-off who sleeps with his mother and molests children. Amusing. I guess you would be the only one who knew that...
Re:wtf? by clone53421 · 2010-07-29 08:42 · Score: 1

When looking at the hand, string, rock system as described, my hand and the string both experience a Centrifugal Force (put a spring in there and prove it).
No, they are experiencing the inertia of the rock pulling back against the centripetal force.
What you are calling centrifugal force is nothing more than a fancy name for the inertia of a rotating object.

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Alexander Peter Kristopeit bought his basement from his mommy for one dollar.

Obvious by wcrowe · 2010-07-29 09:44 · Score: 3, Funny

A new study reveals that the faster it goes, the more squashed it gets.

Well duh. Of course it does. Anyone who has watched a Roadrunner cartoon knows that.

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Proverbs 21:19

Re:Isn't the center of a golf ball a rubberband ba by teebob21 · 2010-07-29 10:31 · Score: 1

Of course - golf balls do change shape, just not while freely rolling. In my case, it's about 100 times every round of 18. Case in point: http://www.golf-simulators.com/images/BallCompression.jpg

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khasim (12/9/06): In a blind taste test, more people preferred Coke over the Pepsi that I had previously pissed in.

practical application by Anonymous Coward · 2010-07-29 10:40 · Score: 0

I'm sure there's a practical application for that! profit!

Notice the experiment setup by pikine · 2010-07-29 12:14 · Score: 1

The shape deformation is caused by the centrifuge that spins the rubber band, as a result of that particular experiment setup. I argue that no such deformation would happen if you use a treadmill instead.

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I once had a signature.

Not modern physics ... by frogzilla · 2010-07-29 12:23 · Score: 1

When a physicist says "modern physics" nothing as large as elastic bands is ever involved.

Re:Not modern physics ... by WolfWithoutAClause · 2010-07-30 04:47 · Score: 1

Modern physics presumably includes chaos theory, and chaos theory applies just fine to non linearities in elastic bands.

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-WolfWithoutAClause
"Gravity is only a theory, not a fact!"

Ob: XKCD. by aug24 · 2010-07-29 21:41 · Score: 1

Tell him he's a twat: http://xkcd.com/123/

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You're only jealous cos the little penguins are talking to me.

OK, At least two problems with this anaylysis by gurutc · 2010-07-30 01:23 · Score: 1

Ok, At least two problems with this analysis.

1. How about heat from flexing that lowers the stiffness and allows more the top of the band to sag as speed increases. If this test was properly designed however, the sag from this effect would be countered by #2 below:

2. Doing this test in a drum means that there's no airflow over the top of the rubber band. If the band was rolling downhill at speed, the top of the rubber band would acquire an attached airflow creating lift due to the bernoulli effect. This would cause the top of the rubber band to bow upwards.

I'm amazed that no mention or consideration is made of either of these points.

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Moderation in All Things... Especially Moderation - gurutc

Re:OK, At least two problems with this anaylysis by smallshot · 2010-07-30 04:13 · Score: 1

Yeah, I'm thinking either they haven't considered a lot of things in this experiment, or they're keeping all the data to themselves until they can prove their speculations. I also hope they tested this with different elasticity coefficients and weights to be thorough.
To be honest, the results they are describing just make sense to me given what we already know about elasticity.. imagine the rubber band was made up of tiny links (like a the tread on a tank) and they were connected with the appropriate elasticity coefficient (that changes with the application of heat). I'm pretty sure if you model that you'll see that it's not so complicated after all.

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The Physics of a Rolling Rubber Band

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