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afrikab
in skating, what happens when angular momentum is conserved?
For skating, if you spread your arms, you slow down (because your moment of inertia increased). If you bring your body into a smaller shape, the moment of inertia decreases, so your angular velocity increases.
The conservation of angular momentum explains the angular acceleration of an ice skater as she brings her arms and legs close to the vertical axis of rotation. By bringing part of mass of her body closer to the axis she decreases her body's moment of inertia. Because angular momentum is constant in the absence of external torques, the angular velocity (rotational speed) of the skater has to increase.