Question

A solid sphere is rotating in free space. If the radius of the sphere is increased, keeping its mass the same, which one of the following will not be affected?

• A. Moment of inertia
• B. Angular momentum
• C. Angular velocity
• D. Rotational kinetic energy

Answer 1

The correct option is B Angular momentum

Since no torque acts on the sphere, its angular momentum $L=\left(I\omega \right)$ remains unchanged, where I is the moment of inertia and ω is the angular velocity of the sphere. If the radius of the sphere is changed, I and hence ω will both change. Also, rotational kinetic energy $(=\frac{1}{2}I{\omega }^2)$ will also change.