Law of conservation of angular momentum

Definition

The law of conservation of angular momentum states that if no external torque acts on a system, the total angular momentum of the system remains constant. This principle is fundamental in analyzing rotational motion and interactions.

5 Must Know Facts For Your Next Test

1. Angular momentum is given by the product of moment of inertia and angular velocity: $L = I \omega$.
2. In a closed system with no external torques, the initial angular momentum equals the final angular momentum: $L_{initial} = L_{final}$.
3. This law explains phenomena like why a figure skater spins faster when pulling their arms inward.
4. Angular momentum is a vector quantity, having both magnitude and direction.
5. It applies to various systems such as planets orbiting stars, rotating wheels, and atomic particles.

Review Questions

• What happens to the angular velocity of a rotating object if its moment of inertia decreases while conserving angular momentum?
• Explain how the conservation of angular momentum affects an ice skater's spin when they pull their arms in close to their body.
• How does external torque influence the conservation of angular momentum in a system?

Related terms

Moment of Inertia:

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

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.