Angular momentum

Definition

Angular momentum is a measure of the quantity of rotation of an object and is a vector quantity. It is given by the product of the moment of inertia and angular velocity.

5 Must Know Facts For Your Next Test

1. Angular momentum ($\vec{L}$) is conserved in a closed system with no external torques.
2. The formula for angular momentum is $\vec{L} = I \vec{\omega}$, where $I$ is the moment of inertia and $\vec{\omega}$ is the angular velocity.
3. Angular momentum has both magnitude and direction, making it a vector quantity.
4. The unit for angular momentum in the International System (SI) is kilogram meter squared per second (kg·m²/s).
5. In rotational motion, torque ($\tau$) causes a change in angular momentum according to $\tau = \frac{d\vec{L}}{dt}$.

Review Questions

• What are the units for measuring angular momentum?
• How does torque affect angular momentum?
• Explain how conservation of angular momentum works in a closed system.

Related terms

Moment of Inertia:

A measure of an object's resistance to changes in its rotational motion, dependent on mass distribution relative to the axis of rotation.

Torque:

A force that causes rotation, calculated as the product of force and lever arm distance from the axis of rotation.

Angular Velocity:

The rate at which an object rotates or revolves around an axis, measured in radians per second (rad/s).