5) Angular Momentum

Question 1

State the law of conservation of angular momentum.

Answer 1

The total angular momentum of a system remains constant provided no external torque acts on the system.

Question 2

Explain why the period of rotation of the star decreases as it becomes smaller.

Answer 2

• As the radius decreases, the moment of inertia of the star decreases.
• Iω must remain constant.
• I decreases so ω increases and a greater ω means a shorter period of rotation.