A ballerina stretches her hands out while spinning and then pulls them closer to her body. What happens to her angular v

Question

A ballerina stretches her hands out while spinning and then pulls them closer to her body. What happens to her angular velocity when she pulls her hands in?

Accepted Answer

By pulling her hands in, mass is distributed closer to the axis of rotation, decreasing her moment of inertia ($I$). Since angular momentum $L = I\omega$ is conserved, decreasing $I$ causes the angular velocity $\omega$ to increase.

System of Particles and Rotational Motion

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