Question

A solid cylinder and a hollow cylinder, each of mass \( M \) and radius \( R \), are rotating with the same angular velocity \( \omega \). What is the ratio of their rotational kinetic energies \( \left( \frac{K_{\text{hollow}}}{K_{\text{solid}}} \right) \)?

• A. 1
• B. 2
• C. 3
• D. 3/2

Hint:

For rotating bodies, the moment of inertia depends on their mass distribution. The solid cylinder has less moment of inertia than the hollow cylinder, hence its rotational kinetic energy is half of the hollow cylinder's.