Angular momentum is

Angular momentum is the primary concept that gives a description of rotational motion within any object. The quantity is a vector, and hence it has both magnitude and direction. The angular momentum depends on two factors: moment of inertia and angular velocity. The moment of inertia is a form of quantifying the distribution of mass with respect to the axis of rotation of an object, while the angular velocity gives a description of how fast an object is rotating.

In a closed system, the total angular momentum remains unchanged if no net torque is acting upon it. This principle is often termed the law of conservation of angular momentum and is particularly important in the examination of the motion of rotating bodies. For example, if a figure skater pulls her arms in during the spin she performs, her moment of inertia decreases, causing her angular velocity to increase and, hence, keeping the angular momentum unchanged.

There is a calculation of angular momentum for various shapes like disks, spheres, and rigid bodies. It has been very fundamental in understanding the phenomena of planetary motion, for instance, because the angular momentum of celestial objects remains constant when they orbit other larger masses. Angular momentum generally plays a fundamental role in classical and modern physics in terms of dynamics in rotating systems and the universal laws governing the motion.

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