Angular momentum conservation is one of the most fundamental laws in physics. It describes how the rotational motion of objects behaves when no external forces interfere. The angular momentum of a particle is defined as the cross product of its position vector and linear momentum.
The conservation principle states that when no external torque acts on a system, the total angular momentum remains constant throughout the motion. This fundamental law means that L initial equals L final, regardless of how the system's configuration changes over time.
A classic example of angular momentum conservation is a figure skater spinning. When the skater extends their arms, they have a large moment of inertia and spin slowly. But when they pull their arms close to their body, the moment of inertia decreases, and to conserve angular momentum, they must spin faster.