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F = ma (11–17)
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FMA-2020A-13 · 2020A F = ma (AAPT)

2020 F = ma Exam A — Question 13

A ballerina with moment of inertia I is quickly twirling with angular velocity ω. In her hand she has a pen of mass m at a radius R from her axis of rotation. The ballerina releases the pen. Afterward, what happens to the vertical component of the angular momentum of the system consisting of the ballerina and the pen? You may ignore all friction, but not gravity or normal forces.
Source: Question 13, 2020 F = ma Exam A, © 2020 American Association of Physics Teachers (AAPT) and the U.S. Physics Team. Adapted by PhysicsTrainer: reformatted into a separate question and answer choices for online multiple-choice practice; any shared setup from nearby questions is repeated here. Not affiliated with or endorsed by AAPT or the U.S. Physics Team.