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# hmwk9_aps - shooting foot. What is the physics explanation...

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Homework #9 Due midnight Sunday November 20. 1. An ice skater pulls her arms in to spin faster. (a) Explain in terms of conservation of angular momentum why she spins faster. (Use a physics equation.) (b) Is her rotational kinetic energy larger or smaller? (Explain using a physics equation.) was done. Explain in words what force and what distance was in- volved. 2. Consider the dive analyzed in Fig. 6-36. (a) In words, what quantity does not change during the dive? What symbol does Hay use for this quantity? What symbol do Professors Heidbrink and McWilliams use? (b) When is the angular velocity largest? When is the rotational inertia largest? 3. For a powerful shot, a soccer player a) drives the upper leg forward then whips the lower leg at the knee, b) strikes the ball with a stiﬀ ankle c) on the top of the foot (“the laces”), d) following through to land on the
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Unformatted text preview: shooting foot. What is the physics explanation for each of these? If the shooter wants the shot to curve, what else must he do? 4. There are three diﬀerent types of “sweet spot.” Describe each type in physics language. 5. If a tennis player is having trouble controlling the angle of her shots, how should she alter her racket? If she wants more “power” (not the physics deﬁnition) and is having no diﬃculty swinging in time, what change in racket would you suggest? Warmup Question Submit answers by 11:00 p.m. Monday November 21. 1. Warmup question for November 22. In football, why is a place kicker more likely to make a long ﬁeld goal attempt if he kicks a spiral (rather than a tumble)? If he kicks in Denver (rather than in San Diego)? 1...
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## This note was uploaded on 12/12/2011 for the course PHYS 17 taught by Professor Mcwilliams,r during the Fall '08 term at UC Irvine.

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