Question

State the law of conservation of angular momentum and explain with a suitable example.

Answer 1

Statement: The angular momentum of a body remains constant if the resultant external torque acting on the body is zero.

Example:

1. A ballet dancer makes use of the law of conservation of angular momentum to vary her angular speed.
2. The torque acting on her body is zero. By the law of conservation of angular momentum, L = constant
   Iω = constant ⇒ ω ∝1/I
3. When she suddenly folds her arms and brings the stretched leg close to the body, her angular velocity increases on account of the decrease in moment of inertia. This helps in rotating safely on her legs.