What’s the physics of rotational force?

Question

Also, why do you spin faster when you bring your arms in?

In: Physics

Answer 1

You have the same energy in the rotating object if it has a radius of x or 2x.

But remember, a larger radius has a higher velocity for the same angular change as a shorter radius. So in this case the energy isn’t changing, but the object has a shorter distance to travel per rotation, so the angular velocity increases. If you extend back out, there is a larger distance to cover with the same energy available, so angular velocity slows down.