Question

Explain how a figure skater uses the concept of angular momentum to control her angular speed , when she is spinning.

Answer 1

Unless there is an external torque, the angular momentum of the body will not change. In case of the figure skater, in order to increase the angular velocity, the skater will bring her hands close to the body. The reason behind this is as there is no external force, the angular momentum will be conserved (it will be a constant).

L = Iw

where L = angular momentum, I = moment of inertia, w = angular speed.

By bringing the hands close to the body, the moment of inertia of the figure skater will decrease, and to maintain the angular momentum the angular speed will increase.

And when the skater has to decrease the angular speed, the skater will open her hands, this will increase her moment of inertia and the angular speed will decrease. In this way, the figure skater will control her angular speed.

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