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Unformatted text preview: Because there are no non-conservative 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