angular momentum

American  

noun

Physics.

1. the product of the moment of inertia of a body about an axis and its angular velocity with respect to the same axis.

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angular momentum British  

noun

1. a property of a mass or system of masses turning about some fixed point; it is conserved in the absence of the action of external forces

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angular momentum Scientific  

/ ăng′gyə-lər /

1. A measure of the momentum of a body in rotational motion. The angular momentum of rigid bodies is conserved; thus, a spinning sphere will continue to spin unless acted on by an outside force. Changes in angular momentum are equivalent to torque. In classical mechanics, angular momentum is equal to the product of the angular velocity of the body and its moment of inertia around the axis of rotation. It is a vector quantity; the vector points up along the axis of counterclockwise rotation. In quantum mechanics, the angular momentum of a physical system is quantized and can only take on discrete values.

2. See also Planck's constant spin

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Etymology

Origin of angular momentum

First recorded in 1865–70

Example Sentences

As angular momentum moved from one vibration to another, the direction of rotation flipped.

From Science Daily • May 24, 2026

An international team of researchers has directly observed how angular momentum moves through a crystal lattice for the first time, revealing an unexpected quantum effect that causes the direction of rotation to reverse.

From Science Daily • May 24, 2026

Although Umklapp processes are already known in other areas of condensed matter physics, this is the first experimental demonstration involving lattice angular momentum.

From Science Daily • May 24, 2026

One promising direction is a field called orbitronics, which focuses on using the motion of electrons around an atom's nucleus, known as orbital angular momentum, to carry and store information more efficiently.

From Science Daily • Apr. 19, 2026

Conservation of angular momentum is your best friend.

From "Legendary Frybread Drive-In" by Cynthia Leitich Smith