Angular momentum

Science

Definition

Angular momentum is the rotational equivalent of linear momentum, describing how much rotational motion an object has. It depends on the object's moment of inertia and angular velocity, and it is conserved in a closed system with no external torques.

Examples

  • A figure skater spins faster by pulling their arms in, decreasing moment of inertia while conserving angular momentum
  • Earth's angular momentum keeps it spinning at a nearly constant rate on its axis
  • A spinning gyroscope resists changes to its orientation due to conservation of angular momentum
Key Fact

L = Iω; angular momentum is conserved when net external torque = 0.

Related Terms

Angular velocity Rotational inertia Torque Conservation of momentum

Study This Concept

Practice angular momentum with free review games in these units:

AP Physics 1 Unit 5: Rotational Motion