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Unformatted text preview: Because there are no nonconservative forces, the total amount of mechanical energy remains constant. 52. We can answer this question by calculating the power exerted by each of them. For Valerie we have 1200 J ÷ 10 s = 120 watts, and for Brett we have 5000 J ÷ 50 s = 100 watts. Therefore, Valerie is more “powerful.” Exercise 20. Let’s choose the gravitational potential energy to be zero at the level of the sidewalk. a) ( 29 ( 29 ( 29 2 0.1kg 10 m s 5 m 5 J GPE mgh = = = b) zero, by our choice for the zero level. c) KE GPE ∆ + ∆ = ( 29 5 J 6 J 11 J f i KE GPE KE =  ∆ + =  + = Note that the answer to this part of the question does not depend on our choice for the zero of gravitational potential energy. The ball initially has 6 J of kinetic energy and it gains 5 J of kinetic energy as it falls. d) Because the initial kinetic energy is independent of direction, the answer to part c) would not change....
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This document was uploaded on 10/29/2011 for the course PHSX 103 at MSU Bozeman.
 Fall '02
 GregoryFrancis

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