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A gymnast is spinning with her arms and legs fully extended. When she draws her arms and legs inward, what happens?

1. Her angular velocity decreases
2. Her moment of inertia decreases
3. Her angular velocity remains unchanged
4. Her angular momentum increases

Correct answer: Her moment of inertia decreases

Solution

Bringing arms and legs inward reduces the distribution of mass about the spin axis, so the moment of inertia decreases. With angular momentum conserved, the angular velocity correspondingly increases.

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