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An ice-skater starts to spin while standing upright with her arms fully extended outward. In each...

An ice-skater starts to spin while standing upright with her arms fully extended outward. In each of her hands she holds a 1.0-kg dumbbell. Model her body as a 50-kg, 0.20-m–radius cylinder, her arms as uniform 2.0-kg, 0.75-m–long, 0.10-m diameter rods, and the dumbells as point masses. She then draws her arms downward, until they are by her sides, 0.20 m from her axis of rotation. (a) What is her initial moment of inertia? (b) What is her final moment of inertia when her arms are fully downward? (c) If her initial rotation frequency is 1.0 Hz, what is her final rotation frequency?

Correct answer (a) 4.3 kg•m2; (b) 1.4 kg•m2; (c) 3.1 Hz

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