Angular momentum

Angular momentum is a vector quantity that measures rotational motion. It depends on an object's mass distribution, motion, and choice of reference point.

Torque: Torque is the rate of change of angular momentum and a measure of a force's tendency to rotate an object. Torque changes angular momentum, just as force changes linear momentum.
Linear momentum: Linear momentum is the product of an object's mass and velocity. Angular momentum is its rotational counterpart, defined relative to a chosen origin.
Precession: Precession is the gradual change in the direction of a rotating body's axis under an applied torque. A torque redirects angular momentum, producing the characteristic motion of a tilted spinning top.
Angular velocity: Angular velocity is the rate and direction of change of angular position. It describes rotational rate, while angular momentum also depends on inertia.
Moment of inertia: Moment of inertia measures how an object's mass is distributed relative to a rotation axis. For a rigid body rotating about a fixed principal axis, angular momentum depends on this rotational inertia.
Cross product: The cross product is a vector operation that produces a vector perpendicular to two input vectors. The position–momentum cross product defines angular momentum for a point particle.
Figure skating spin: A figure skating spin is rapid rotation performed on the ice, often with changing body posture. Pulling the limbs inward reduces rotational inertia and increases spin rate when external torque is small.
Rotational energy: Rotational energy is the kinetic energy associated with rotation. A rotating body can have the same angular momentum as another but different rotational energy.
Conservation of angular momentum: Angular momentum remains constant in a system with zero net external torque. This principle explains why rotational motion persists when external torque is absent.
Position vector: A position vector specifies an object's location relative to a chosen origin. Changing the origin can change a system's angular momentum.

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