317_Physics ProblemsTechnical Physics

317_Physics ProblemsTechnical Physics - Chapter 10 P10.84(a...

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Chapter 10 319 P10.84 (a) The mass of the roll decreases as it unrolls. We have m Mr R = 2 2 where M is the initial mass of the roll. Since E = 0, we then have ∆∆ UK K g ++ = trans rot 0. Thus, when I mr = 2 2 , mgr MgR mv mr −+ + L N M O Q P = bg 22 2 2 0 ω Since rv = , this becomes v gR r r = 4 3 33 2 ej (b) Using the given data, we find v 531 10 4 . m s (c) We have assumed that E = 0. When the roll gets to the end, we will have an inelastic collision with the surface. The energy goes into internal energy . With the assumption we made, there are problems with this question. It would take an infinite time to unwrap the
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