Question

Explain how a ballet dancer uses this law to change her angular speed.

Answer 1

Ice skater or ballet dancer spins quickly by drawing arms close to body.

As the skater begins a spin, she stretches her arms and back out and away from her body to create a slow spin. As she reaches the end of the spin, she tucks her arms in and tightens her frame, causing her to spin much more rapidly. She has consolidated her mass closer to the axis, reduced her moment of inertia, and reduced the effort needed to spin quickly. With no change in force, she is able to accelerate her rotational speed.

torque = moment of inertia x angular acceleration

angular momentum = moment of inertia x angular speed