Question

A person is standing on a moving platform spreading his arms. He suddenly contracts his rms, his:

• A. angular momentum will increase.
• B. moment of inertia will increase.
• C. moment of inertia will decrease.
• D. angular momentum remains same.

Answer 1

Answer: (D)

Angular momentum $J=I\omega .$ On stretching the arm, their is no effect on $I$ and $\omega ,$ therefore, angular momentum remains same.