Question

An ice skater spins with his arms outstretched. When he pulls his arms in and raises them above his head he spins much faster than before. Did a torque act on the ice skater? If not how could his angular velocity have increased?

Answers

No torque was exerted on the skater to increase the spin rate. The angular momentum I*w remained the same. The angular velocity w increased while the moment of intertia (I) decreased.
Thank you.

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