Angular momentum:

The strength of a rotation is called torque. In everyday life it is often called drive.

The angular momentum does not change, if there is no external impact of a torque, which means, that there is no impact of a force on a lever arm.

So if there is no impact of external forces, the angular momentum of a physical system is conserved. This is what is defined in the law of conservation of angular momentum.

The angular momentum L can be calculated from the angular velocity ω and the moment of inertia J relative to the axis of rotation.

L	angular momentum
J	moment of inertia
ω	angular velocity

If the moment of inertia J decreases, the angular velocity ω will increase in case of constant angular momentumL.