# Quiz2 - vertical rotation axis is conserved f f i i I I ω...

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PHY126 Quiz No. 2 (Chap.11) Name: A skater’s body has rotational inertia 4.2 kg m 2 with his fist held to his chest and 5.7 kg m 2 with arms stretched. The skater is twirling at 3.0 rev/s while holding a 2.5-kg weight in each outstretched hand; the weights are 76 cm from his rotation axis. If he pulls his hands in to his chest, how fast will he be twirling? Solution: If the skater is twirling on frictionless horizontal ice, his angular momentum about the
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Unformatted text preview: vertical rotation axis is conserved, f f i i I I ω = . The rotational inertia is that of the skater’s body plus for the weights, and if we assume that the latter are essentially pulled into the axis of rotation, . 2 2 mr rev/s 13 . 6 2 . 4 / ] 6) 2(2.5)(0.7 rev/s)[5.7 3 ( ) / ( 2 = + = = f i i f I I...
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