I thought you might say that, which is why I introduced the electromagnet example. Potential energy is not real energy (otherwise every single metal thing in the universe would have all of this energy corresponding to every magnet in existence). Kinetic energy is real though.
When the electromagnet is off, the ball has no potential energy with respect to it. It doesn't seem to make sense that flipping the switch will impart energy to all metal objects in the vicinity (or in the universe). I suspect that one would find the magnet's battery depleted by exactly the amount of kinetic energy that the ball gained (minus any other transmission losses etc.). Is this true? If so, what is the equivalent 'power' for non-electro magnets?
I have a magnet which I had when I was little, and it is now much weaker. So magnets can get weaker (and if there had been a ball fixed at a set distance from it over these years, the ball would gradually lose potential energy). Magnetism is an effect of small electric currents within the magnet; doesn't it stand to reason that when the magnet is used, it could lose power by disturbing some of those currents?
PS. thanks for persevering with my lack of understanding.
MAF? ITYM AFM (woohoo, I started a post with 3 acronyms). There are two common air sensing systems for fuel-injected engines: MAP (manifold absolute pressure) and AFM (air flow meter). I think the latter is what you are describing. The problem with it is that the CPU can calculate it instantly, as you say, but the sensor is near the start of the air intake, which can be several metres away from the point of injection (on a turbo car), so it is using slightly out of date data, so it can make all sorts of mistakes (eg. if you boost then brake hard on a turbo with AFM it is liable to stall as you brake because the engine floods with all the fuel that was meant for the boosting). If I were designing this black box , I would hook it up to the speed sensor on the gearbox, the same way that your dash speedo works. (Practically speaking, make it read off the dash speedo). Of course, the AFM output could still be stored.
What if it was stuck at 88? Then you just have to say 'I have fresh Plutonium in my Flux Capacitor, Sir!!' and it will prove you were not going that fast. Cogito ergo sum. etc.
This doesn't violate the laws of thermodynamics any more than putting a metal ball near a magnet and watching it "suddenly gain kinetic energy from nowhere". Or alternatively, putting it near an electromagnet that's turned off, and then turn on the magnet. Obviously the energy for the ball's motion came from the power that powers the magnet... ie. from the magnet. Equally obviously, these motors would run for some time and the magnets would get less and less powerful until they ran out.
Oh come on. Conservation of energy. "Crack"ing the water molecule must take at least as much energy as is released when the oxygen and hydrogen recombine. So at worst, the water will have no effect. It won't fuel the fire.
With college math, I had the same disenchantment as you. There are some courses that are more insight-y (eg. analysis) and less so (eg. partial differential equations). But this is not a reason to lose heart. You cannot apply insight if you have not first fully grokked the available tools. Part of training for IMO geometry problems is learning dozens of theorems and tidbits of information (eg. incircle, circumcircle, triangle equalities, sin & cos formulae, sin 2A, similar triangles, that one about the fractions of each edge multiplying to -1, and so on). Then to solve the problem you try things until you strike an 'aha' that resolves the problem into these simple units you have already learned. The thing with college math is that it is a whole new bunch of "simple units" to learn. Once you have done grind work to grok eigenvectors and orthogonal basis vectors, for example, then you can suddenly "aha-solve" a whole new class of problems (eg. unitary evolution in quantum physics) by slapping such a basis on them.
Now for the real question:
how did you work it out?
It only took me about 2 seconds to get the answer, but I would be at a loss to try and say how I did it, or how to explain to someone else how they could work it out in a similar timeframe.
If I were writing a computer program, I would take a dictionary, look for words matching "pine(.*)", then see if "sauce\1" or "\1sauce" and "crab\1" or "\1crab" were also in the dictionary. However it just doesn't seem that this is the way that my brain worked it out. I say this because the same 'technique' would apply to more obfuscated situations, eg. if it had been "piny", "crabby", "saucy" then we would still have found the solution in the same time frame.
If I had not seen the solution in a few seconds, I would have begun trying this algorithm consciously. But even in this case, there is the 'aha' moment when you try "pineapple" and realise without further conscious effort that it is correct.
About time. I hate finding out just what is supposedly in my insurance policy, after it's too late, and having to jump through hoops to get clauses added.
Han-Wen says: In my opinion, any file format that claims to be universal should have two properties: it should have an expressive structure, so other formats can be expressed in it, and it should be as lean as possible, so that converting from other formats amounts to removing information.
I assume this guy didnt design GIF or PNG then (might have designed JPEG).. I hope he never designs a text file format!
Slashdot Mirror
Ugh, I had a feeling it would be something like that. Oh well, off to misheardlyrics.com :) (or whatever)
Thanks, that's what I was getting at (I think!). However I have no idea just how long it would take for the magnets to 'run down'.
I thought you might say that, which is why I introduced the electromagnet example. Potential energy is not real energy (otherwise every single metal thing in the universe would have all of this energy corresponding to every magnet in existence). Kinetic energy is real though.
When the electromagnet is off, the ball has no potential energy with respect to it. It doesn't seem to make sense that flipping the switch will impart energy to all metal objects in the vicinity (or in the universe). I suspect that one would find the magnet's battery depleted by exactly the amount of kinetic energy that the ball gained (minus any other transmission losses etc.). Is this true? If so, what is the equivalent 'power' for non-electro magnets?
I have a magnet which I had when I was little, and it is now much weaker. So magnets can get weaker (and if there had been a ball fixed at a set distance from it over these years, the ball would
gradually lose potential energy).
Magnetism is an effect of small electric currents within the magnet; doesn't it stand to reason that when the magnet is used, it could lose power by disturbing some of those currents?
PS. thanks for persevering with my lack of understanding.
MAF? ITYM AFM (woohoo, I started a post with 3 acronyms). There are two common air sensing systems for fuel-injected engines: MAP (manifold absolute pressure) and AFM (air flow meter). I think the latter is what you are describing. The problem with it is that the CPU can calculate it instantly, as you say, but the sensor is near the start of the air intake, which can be several metres away from the point of injection (on a turbo car), so it is using slightly out of date data, so it can make all sorts of mistakes (eg. if you boost then brake hard on a turbo with AFM it is liable to stall as you brake because the engine floods with all the fuel that was meant for the boosting).
If I were designing this black box , I would hook it up to the speed sensor on the gearbox, the same way that your dash speedo works. (Practically speaking, make it read off the dash speedo). Of course, the AFM output could still be stored.
What if it was stuck at 88? Then you just have to say 'I have fresh Plutonium in my Flux Capacitor, Sir!!' and it will prove you were not going that fast. Cogito ergo sum. etc.
Oh come on. If this guy goes to jail then Ken Lay[*] should too[**].
[*] I have no idea who Ken Lay is but everyone was going on about him in the article about the movie recording.
[**] Hopefully the movie guy will "get Lay-ed" , so to speak
Are you the real David Hume? (as in, David Hume could out-consume poor old private Schlegel, etc.)
This doesn't violate the laws of thermodynamics any more than putting a metal ball near a magnet and watching it "suddenly gain kinetic energy from nowhere". Or alternatively, putting it near an electromagnet that's turned off, and then turn on the magnet. Obviously the energy for the ball's motion came from the power that powers the magnet... ie. from the magnet.
Equally obviously, these motors would run for some time and the magnets would get less and less powerful until they ran out.
After depositing an oil slick in that ocean, of course.
#define GN atof(gets(b)) // Read a float from stdin
char b[99];
So now we know, to crash the raytracer just enter 99 characters! (or even, a value outside the allowed range for floats.)
These macros (except perhaps RP) are all execrable. What a great way to say "Dont hire me for any serious project!"
Oh come on. Conservation of energy. "Crack"ing the water molecule must take at least as much energy as is released when the oxygen and hydrogen recombine. So at worst, the water will have no effect. It won't fuel the fire.
IMO: good on you, I went too :) (Mumbai, 1996)
With college math, I had the same disenchantment as you. There are some courses that are more insight-y (eg. analysis) and less so (eg. partial differential equations). But this is not a reason to lose heart. You cannot apply insight if you have not first fully grokked the available tools. Part of training for IMO geometry problems is learning dozens of theorems and tidbits of information (eg. incircle, circumcircle, triangle equalities, sin & cos formulae, sin 2A, similar triangles, that one about the fractions of each edge multiplying to -1, and so on). Then to solve the problem you try things until you strike an 'aha' that resolves the problem into these simple units you have already learned.
The thing with college math is that it is a whole new bunch of "simple units" to learn. Once you have done grind work to grok eigenvectors and orthogonal basis vectors, for example, then you can suddenly "aha-solve" a whole new class of problems (eg. unitary evolution in quantum physics) by slapping such a basis on them.
Now for the real question:
how did you work it out?
It only took me about 2 seconds to get the answer, but I would be at a loss to try and say how I did it, or how to explain to someone else how they could work it out in a similar timeframe.
If I were writing a computer program, I would take a dictionary, look for words matching "pine(.*)", then see if "sauce\1" or "\1sauce" and "crab\1" or "\1crab" were also in the dictionary.
However it just doesn't seem that this is the way that my brain worked it out. I say this because the same 'technique' would apply to more obfuscated situations, eg. if it had been "piny", "crabby", "saucy" then we would still have found the solution in the same time frame.
If I had not seen the solution in a few seconds, I would have begun trying this algorithm consciously. But even in this case, there is the 'aha' moment when you try "pineapple" and realise without further conscious effort that it is correct.
This is such a kickass book. I can't endorse it highly enough. I believe there are actually 2 of them (a blue one and a green one, or something).
Has anyone noticed that USTR is only 1 place in the alphabet different to USSR ?
The Trogdor game!
Slashdot is full of flames about capitalism..
Come on, this is just comparing Appels and oranges
We've had a TV newsreader called "Richard Long" for the last 20 years or so. (Although recently he got fired for "poor performance" .. go figure)
And your second-born, "Oops I did it again"
Could be a blessing in disguise - code without pointers is usually a lot better than the same code with pointers.
About time. I hate finding out just what is supposedly in my insurance policy, after it's too late, and having to jump through hoops to get clauses added.
What if the other formats do not have any redundant information?
Han-Wen says: In my opinion, any file format that claims to be universal should have two properties: it should have an expressive structure, so other formats can be expressed in it, and it should be as lean as possible, so that converting from other formats amounts to removing information.
I assume this guy didnt design GIF or PNG then (might have designed JPEG)
Perhaps that is what it was originally. Nowadays, it is a security feature.