Comments on: Problem with energy conservation law? http://www.energy--talk.com/creative-energy-ideas/problem-with-energy-conservation-law/207/ How Can We Be More Energy Efficient? Wed, 08 Sep 2010 13:55:44 +0000 http://wordpress.org/?v=2.6.5 By: C Anderson http://www.energy--talk.com/creative-energy-ideas/problem-with-energy-conservation-law/207/#comment-395 C Anderson Fri, 17 Oct 2008 16:35:26 +0000 http://www.energy--talk.com/creative-energy-ideas/problem-with-energy-conservation-law/207/#comment-395 Mass differential is assumed in the forming of the problem / question by the use of metal vs. tennis balls. You don't need to know the specific mass -- they're trying to get you to assume it, and also to assume the steel ball isn't a tiny little thing, else this problem wouldn't make any sense. It requires only a tiny fraction of the kinetic energy of the steel ball, imparted to the tennis ball, to get the tennis ball to bounce (due to its rebound from compression) quite high. The steel ball as a great deal of kinetic energy since it is of high mass. The tennis ball requires very little new KE to move it quite a distance since it is so light. In short, while the steel ball may bounce back to nearly its original height, it takes only a tiny fraction of the steel ball's huge kinetic energy to really move that tennis ball... so little that the results would hardly be noticed in the rebound of the steel ball. Mass differential is assumed in the forming of the problem / question by the use of metal vs. tennis balls. You don’t need to know the specific mass — they’re trying to get you to assume it, and also to assume the steel ball isn’t a tiny little thing, else this problem wouldn’t make any sense.

It requires only a tiny fraction of the kinetic energy of the steel ball, imparted to the tennis ball, to get the tennis ball to bounce (due to its rebound from compression) quite high. The steel ball as a great deal of kinetic energy since it is of high mass. The tennis ball requires very little new KE to move it quite a distance since it is so light.

In short, while the steel ball may bounce back to nearly its original height, it takes only a tiny fraction of the steel ball’s huge kinetic energy to really move that tennis ball… so little that the results would hardly be noticed in the rebound of the steel ball.

]]> By: Bekki B http://www.energy--talk.com/creative-energy-ideas/problem-with-energy-conservation-law/207/#comment-394 Bekki B Fri, 17 Oct 2008 15:00:49 +0000 http://www.energy--talk.com/creative-energy-ideas/problem-with-energy-conservation-law/207/#comment-394 You are correct. It depends on what nearly 1 meter means. If the heavy metal ball doesn't bounce all the way back up, there's some energy that could be turned into heat or tennis ball energy. You need more info to numerically handle this problem. You are correct. It depends on what nearly 1 meter means. If the heavy metal ball doesn’t bounce all the way back up, there’s some energy that could be turned into heat or tennis ball energy. You need more info to numerically handle this problem.

]]> By: misoma5 http://www.energy--talk.com/creative-energy-ideas/problem-with-energy-conservation-law/207/#comment-393 misoma5 Wed, 15 Oct 2008 20:55:01 +0000 http://www.energy--talk.com/creative-energy-ideas/problem-with-energy-conservation-law/207/#comment-393 You have to take into account the weight of both the heavy metal ball and the light tennis ball. As long as the combined energy does not surpass the initial potential energy of the metal ball, no law has been violated. You have to take into account the weight of both the heavy metal ball and the light tennis ball. As long as the combined energy does not surpass the initial potential energy of the metal ball, no law has been violated.

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