Comments on: Question about conservation of energy: How is energy conserved if a rock is dropped from the top of a building http://www.energy--talk.com/creative-energy-ideas/question-about-conservation-of-energy-how-is-energy-conserved-if-a-rock-is-dropped-from-the-top-of-a-building/215/ How Can We Be More Energy Efficient? Thu, 09 Feb 2012 01:04:20 +0000 http://wordpress.org/?v=2.6.5 By: cluekoo http://www.energy--talk.com/creative-energy-ideas/question-about-conservation-of-energy-how-is-energy-conserved-if-a-rock-is-dropped-from-the-top-of-a-building/215/#comment-407 cluekoo Mon, 24 Nov 2008 14:23:46 +0000 http://www.energy--talk.com/creative-energy-ideas/question-about-conservation-of-energy-how-is-energy-conserved-if-a-rock-is-dropped-from-the-top-of-a-building/215/#comment-407 You are correct in the change from potential energy to kinetic. Once the rock hits the ground, that kinetic energy is also changed into another form. Heat and sound are both correct, but they are relatively weak forms of energy and do not account for all of the energy difference. Much of the energy is indeed transferred through particles as turbulence. Consider a similar scenario. A rock is dropped from a really REALLY high building. Its potential energy gradually converts to kinetic energy. But what happens when it hits terminal velocity? If its velocity no longer increases and as its mass is constant, kinetic energy no longer increases (recall KE = 0.5mv²). Therefore, in this scenario, it is more obvious that the lost potential energy is being transferred into the particles of the air (which are in fact causing the air resistance). You are correct in the change from potential energy to kinetic. Once the rock hits the ground, that kinetic energy is also changed into another form. Heat and sound are both correct, but they are relatively weak forms of energy and do not account for all of the energy difference. Much of the energy is indeed transferred through particles as turbulence.

Consider a similar scenario. A rock is dropped from a really REALLY high building. Its potential energy gradually converts to kinetic energy. But what happens when it hits terminal velocity? If its velocity no longer increases and as its mass is constant, kinetic energy no longer increases (recall KE = 0.5mv²). Therefore, in this scenario, it is more obvious that the lost potential energy is being transferred into the particles of the air (which are in fact causing the air resistance).

]]> By: phdpsychman http://www.energy--talk.com/creative-energy-ideas/question-about-conservation-of-energy-how-is-energy-conserved-if-a-rock-is-dropped-from-the-top-of-a-building/215/#comment-406 phdpsychman Fri, 21 Nov 2008 02:42:43 +0000 http://www.energy--talk.com/creative-energy-ideas/question-about-conservation-of-energy-how-is-energy-conserved-if-a-rock-is-dropped-from-the-top-of-a-building/215/#comment-406 the engery is transferred into heat and sound the engery is transferred into heat and sound

]]> By: physandchemteach http://www.energy--talk.com/creative-energy-ideas/question-about-conservation-of-energy-how-is-energy-conserved-if-a-rock-is-dropped-from-the-top-of-a-building/215/#comment-405 physandchemteach Mon, 17 Nov 2008 16:27:58 +0000 http://www.energy--talk.com/creative-energy-ideas/question-about-conservation-of-energy-how-is-energy-conserved-if-a-rock-is-dropped-from-the-top-of-a-building/215/#comment-405 The energy is passed to the ground in the form of heat. Try this yourself - get two big rocks and keep hitting them together. You will be able to feel a change in the temperature of the areas that are striking each other. Flint is a rock that gives off so much heat when struck that the spark is visible and can be used to start a fire. The energy is passed to the ground in the form of heat. Try this yourself - get two big rocks and keep hitting them together. You will be able to feel a change in the temperature of the areas that are striking each other. Flint is a rock that gives off so much heat when struck that the spark is visible and can be used to start a fire.

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