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.
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.
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?).
That’s a great way to get people to compare themselves to each other, but not a very good way to get them to learn what you objectively call “enough” about the subject. They’re too busy looking at each other’s performance and there’s no reason to be much better than the perceived average.
[Curving a test] makes sure that if the test is biased/bad/improper in spite of multiple checks, top people still compete directly against each other, rather then test itself.
Problem: biased/bad/improper tests inherently reduce the scale size, which then has to be stretched back out again with the curve. It gives an over- or under-exposed picture of the class; it does not give enough contrast between the top-performing students and the bottom ones. You can adjust it to show the contrast between them, but you lose detail. For example, if everyone scores over 90% on a 20-question exam, you have only 3 tiers: 90%, 95%, and 100%. That’s not very descriptive of the relative aptitude of the students for the purpose of grading them, and it’s not very helpful to the students themselves if they want to know what in particular they need to improve on.
Plus, biased/bad/improper tests might not only give inadequate contrast; it might in fact not even test for the correct thing, in which case you can curve it all you want but you still won’t get an accurate representation of the skill that you were supposed to be teaching and testing on.
E was skipped because it already meant “excellent”. D typically means you have to retake the class if it’s a required class for your major, but you might be allowed to not retake it if the class is an elective or outside of your main department. In lower education, D might mean you don’t get held back a year but have to take summer school.
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.
More like the original poster is someone who has had his (or her) CC-licensed images used commercially without permission in the past and went on a fishing expedition to find a few examples of CC-licensed images being used without permission to show how common it is. He never claimed that either image belonged to him and obviously didn’t do due diligence on the Boing Boing picture before assuming that the blogger didn’t have the proper permission to use it.
It makes more sense to teach what needs to be learned, test for it effectively, and THEN set the grades to reflect what was learned.
If you do what I said, that is what you are doing. If you taught the material and tested on it effectively, you would be able to tell from the score whether the student had mastered the information, gained a passable knowledge of it, or failed to understand it to an acceptable level – without normalizing the grade to an average.
Of course, if one school district or state does this, and all the others maintain status quo, it puts those students, even though they may have learned more, at a disadvantage when it comes to college acceptance. I guess that's what makes grade inflation so hard to undo.
That’s what standardized testing is for. I had something like a 3.4 GPA in high school because my curriculum was so difficult, but my ACT score was high enough to impress the college recruiters.
Hmm. To be honest, I don’t like curved grades and even in your case I don’t think a curved grade was the way to go.
A “wake-up call” is a good tool, but I can see a few better ways than scaring everyone into thinking they failed and then basically giving everyone a free exam score after you apply the curve.
a) Make it worth something really trivial, like 2% of the grade – or nothing, even. Make a big deal of the fact that the rest of the exams are going to be just as hard, so they’d better get down to business if they expect to pass the class. Don’t tell them ahead of time how little it’s worth, though, or they’ll blow it off.
b) Allow them to throw out their lowest exam score. Upon going over the syllabus, of course, they’re going to think that they have room to relax because they get a freebie... but the first exam will come as a real surprise and they’ll have to buckle down for the remainder of the class. This is basically the same as option a, but the students will take it more seriously. Plus when you return it, you can tell them outright that this was the entire reason you give them one free exam, as you expect most all of them will be taking this as their freebie, and you hope they all realise that this is serious business now.
If 55% is the average then there's something wrong with what the professor is doing and it is NOT the student's fault.
Maybe, maybe not. Quit assuming you know everything. It’s entirely possible to have an entire class of students who mostly don’t care about school and don’t want to learn – especially in lower learning where they didn’t pay to be there instead of working 8-hour shifts at Wendy’s. Especially if most of them can still get a D and not be held back a year.
Yeah. I’d say that, as it was used in the original quote, it should have been that people want information to be expensive/free.
Information itself doesn’t care whether it is expensive or free (as in beer)... it only wants to be free as in speech, as in once you tell someone something they can then tell someone else and you can’t take it back.
Right. The way I see it... if you license your work then do nothing more than bitch and whine when people trample over that license, you were bluffing. They called your bluff. Nothing more, nothing less.
Absolutely. I guarantee that the publication would quickly find that it was generating less revenue if they randomly picked Goatse or Tubgirl instead of an image that was attractive, appropriate, and added value to the article.
Do you really think these particular images were chosen over others to generate revenue? Or do they just happen to be images picked to go along with the theme of the articles (which is indeed the case)?
Yes to all of the above. What, you think they would have deliberately picked shitty images – to likely damage their reputation and reduce their revenue? They picked images that added value to their product.
Since you don't care in the first place, how is it really hurting you if a company makes a profit? You aren't losing anything.
You did care. You wanted people to have this for free. Then some company came along and tried to cheat people by making them pay for it, and you think you shouldn’t care that the product you created is being used to hurt people?
Except that they go after grandmothers whose grandkids wanted music for their MP3 players, whereas he’s just trying to keep people from profiting off what was supposed to be free (and free under the explicit condition that you weren’t allowed to profit from it).
No, what’s most reasonable is making the tests/classes of the correct difficulty so that someone who ended up with a D deserved the awarded 1.0 grade points and someone with an A deserved 4.0.
Of course, most educators will notice that I said (a) make the tests harder and (b) more work for the teachers (curved tests are easy to write – you don’t have to worry about it being too easy or hard) and stopped listening to my suggestion.
Slashdot Mirror
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.
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...
There can be.
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?).
That’s a great way to get people to compare themselves to each other, but not a very good way to get them to learn what you objectively call “enough” about the subject. They’re too busy looking at each other’s performance and there’s no reason to be much better than the perceived average.
[Curving a test] makes sure that if the test is biased/bad/improper in spite of multiple checks, top people still compete directly against each other, rather then test itself.
Problem: biased/bad/improper tests inherently reduce the scale size, which then has to be stretched back out again with the curve. It gives an over- or under-exposed picture of the class; it does not give enough contrast between the top-performing students and the bottom ones. You can adjust it to show the contrast between them, but you lose detail. For example, if everyone scores over 90% on a 20-question exam, you have only 3 tiers: 90%, 95%, and 100%. That’s not very descriptive of the relative aptitude of the students for the purpose of grading them, and it’s not very helpful to the students themselves if they want to know what in particular they need to improve on.
Plus, biased/bad/improper tests might not only give inadequate contrast; it might in fact not even test for the correct thing, in which case you can curve it all you want but you still won’t get an accurate representation of the skill that you were supposed to be teaching and testing on.
E was skipped because it already meant “excellent”. D typically means you have to retake the class if it’s a required class for your major, but you might be allowed to not retake it if the class is an elective or outside of your main department. In lower education, D might mean you don’t get held back a year but have to take summer school.
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.
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.
Centrifugal force doesn’t exist. It is simply our perception of momentum in a spinning object.
Spinning faster = more velocity perpendicular to slope on the leading edge of the loop. It makes sense that it would flatten out.
More like the original poster is someone who has had his (or her) CC-licensed images used commercially without permission in the past and went on a fishing expedition to find a few examples of CC-licensed images being used without permission to show how common it is. He never claimed that either image belonged to him and obviously didn’t do due diligence on the Boing Boing picture before assuming that the blogger didn’t have the proper permission to use it.
Sorry, not allowed. You said “words”. Now you want to amend that to “non-English words, or English words with unusual etymologies”?
It makes more sense to teach what needs to be learned, test for it effectively, and THEN set the grades to reflect what was learned.
If you do what I said, that is what you are doing. If you taught the material and tested on it effectively, you would be able to tell from the score whether the student had mastered the information, gained a passable knowledge of it, or failed to understand it to an acceptable level – without normalizing the grade to an average.
Of course, if one school district or state does this, and all the others maintain status quo, it puts those students, even though they may have learned more, at a disadvantage when it comes to college acceptance. I guess that's what makes grade inflation so hard to undo.
That’s what standardized testing is for. I had something like a 3.4 GPA in high school because my curriculum was so difficult, but my ACT score was high enough to impress the college recruiters.
Hmm. To be honest, I don’t like curved grades and even in your case I don’t think a curved grade was the way to go.
A “wake-up call” is a good tool, but I can see a few better ways than scaring everyone into thinking they failed and then basically giving everyone a free exam score after you apply the curve.
a) Make it worth something really trivial, like 2% of the grade – or nothing, even. Make a big deal of the fact that the rest of the exams are going to be just as hard, so they’d better get down to business if they expect to pass the class. Don’t tell them ahead of time how little it’s worth, though, or they’ll blow it off.
b) Allow them to throw out their lowest exam score. Upon going over the syllabus, of course, they’re going to think that they have room to relax because they get a freebie... but the first exam will come as a real surprise and they’ll have to buckle down for the remainder of the class. This is basically the same as option a, but the students will take it more seriously. Plus when you return it, you can tell them outright that this was the entire reason you give them one free exam, as you expect most all of them will be taking this as their freebie, and you hope they all realise that this is serious business now.
If 55% is the average then there's something wrong with what the professor is doing and it is NOT the student's fault.
Maybe, maybe not. Quit assuming you know everything. It’s entirely possible to have an entire class of students who mostly don’t care about school and don’t want to learn – especially in lower learning where they didn’t pay to be there instead of working 8-hour shifts at Wendy’s. Especially if most of them can still get a D and not be held back a year.
Yeah. I’d say that, as it was used in the original quote, it should have been that people want information to be expensive/free.
Information itself doesn’t care whether it is expensive or free (as in beer)... it only wants to be free as in speech, as in once you tell someone something they can then tell someone else and you can’t take it back.
Right. The way I see it... if you license your work then do nothing more than bitch and whine when people trample over that license, you were bluffing. They called your bluff. Nothing more, nothing less.
Absolutely. I guarantee that the publication would quickly find that it was generating less revenue if they randomly picked Goatse or Tubgirl instead of an image that was attractive, appropriate, and added value to the article.
Do you really think these particular images were chosen over others to generate revenue? Or do they just happen to be images picked to go along with the theme of the articles (which is indeed the case)?
Yes to all of the above. What, you think they would have deliberately picked shitty images – to likely damage their reputation and reduce their revenue? They picked images that added value to their product.
Since you don't care in the first place, how is it really hurting you if a company makes a profit? You aren't losing anything.
You did care. You wanted people to have this for free. Then some company came along and tried to cheat people by making them pay for it, and you think you shouldn’t care that the product you created is being used to hurt people?
Not free as in beer... free as in speech. Once you let it out, you can’t put the genie back in the bottle.
Except that they go after grandmothers whose grandkids wanted music for their MP3 players, whereas he’s just trying to keep people from profiting off what was supposed to be free (and free under the explicit condition that you weren’t allowed to profit from it).
It should be free... and if you got it for free, it should stay free if you want to redistribute it.
No, what’s most reasonable is making the tests/classes of the correct difficulty so that someone who ended up with a D deserved the awarded 1.0 grade points and someone with an A deserved 4.0.
Of course, most educators will notice that I said (a) make the tests harder and (b) more work for the teachers (curved tests are easy to write – you don’t have to worry about it being too easy or hard) and stopped listening to my suggestion.