What does the principle of conservation of angular momentum state?

The principle of conservation of angular momentum states that the total angular momentum of a closed system remains constant when no external torque is applied. This principle is derived from Newton's laws of motion and reflects the idea that in the absence of external influences, the angular momentum of an object or group of objects will not change over time.

This concept is deeply rooted in physics, particularly in systems involving rotating bodies, such as planets in orbit or figure skaters spinning. When a figure skater pulls in their arms, for example, they reduce their moment of inertia, which results in an increase in their rotational speed, thereby conserving angular momentum.

Understanding this principle is crucial as it allows us to predict the behavior of rotating bodies under various conditions. The situation changes only when external torques act on the system, which can alter the total angular momentum.