Question

A solid sphere is rotating in free space. If the radius of the sphere is increased keeping mass 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

Angular momentum will remain the same since external torque is zero.

$MI$ will increase since $r$ increases ($I=\frac{2}{5}m{r}^2$)

Angular velocity decreases since $L=I\omega$ is conserved.

Rotational KE: $K_{rot}=\frac{L^2}{2I}$ decreases since I increases.