quote:
Originally posted by Volv
With no friction a wheel would continue turning in a vacuum indefinitely (even though there's gravity).
But only if there is a force which starts the motion though, and that's only to begin with. With the chain system depicted above, there isn't such an 'starting' force.
quote:
Originally posted by vaccination
Lol cookie, perpetual motion is possible in a frictionless environment,
Perpetual motion machines aren't possible, not even in theory, not even in a frictionless environment since there should always be an equilibrium of energy. And a perpetual motion machine is exactly based on the nonequilibrium of energy (being it motion energy, heat energy or whatever energy): it produces more energy than you put into it, that's the whole definition of such machines.
The fact that it is said that a perpetual motion machine is not possible in practice is not _just_ because of friction, but mostly because you can not get more energy out of something than you put into it (while preserving its mass). friction is only a tiny part of the problem of perpetual motion machines. Cancelling that out and you would still have the same problems as before: you can not get more energy out of it than you have put into it.
So, forgetting the fact that it isn't possible to completely rule out friction (even with supercooled, superconductors or whatever), thus in a theoretical friction free world, the moment you want to extract energy out of such a perpetual motion machine means that you will eventually loose the stored energy in that machine. And therefore it isn't a real perpetual motion machine to begin with as it will eventually run out.
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There is no more (or less) force pulling on the chain on the left side than there is on the right side, ergo, there is nothing to start movement, ergo there is no movement, even in a theoretical frictionless system, no matter what angle or length the two slopes are, as long as both ends are on the same horizontal plane. The system is always in equilibrium.
I'm (almost) sure that if you take those equations from above and work them further out you would see they are equal (you can in theory because there is always a direct relation between the various elements of the two sides (mass, length, angle, etc), by using ratios instead of real numbers)). The more I think about it the more I am convinced of that.
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