Question

A man spinning in free space changes the shape of his body, e.g., by spreading his arms or curling up. By doing this, he can change his :

• A. moment of inertia.
• B. angular momentum.
• C. angular velocity.
• D. rotational kinetic energy.

Answer 1

Answer: (A), (C), (D)

The correct options are
A moment of inertia.
C angular velocity.
D rotational kinetic energy.

As the moment of inertia is the distribution of mass about the rotational axis, thus a person can change his rotational inertia by spreading or curling his arms. Using the principle of conservation of angular momentum $I_1{\omega }_1=I_2{\omega }_2$, we see that as the moment of inertia varies, the angular velocity varies inversely. Also as the angular velocity varies the rotational kinetic energy also varies.