Chapter 9 - Rotation of Rigid Bodies - Problems - Discussion Questions - Page 294: Q9.17

The change in potential energy of the ball will be converted into rotational kinetic energy of the disk and translational kinetic energy of the ball. Since the moment of inertia of the solid disk is less than the hollow disk, less energy is required to rotate the solid disk. Therefore, more energy can be converted into translational kinetic energy of the ball attached to the solid disk. Since the balls fall the same distance, the change in potential energy is the same for both systems. Therefore, ball A will have more kinetic energy because it is attached to the solid disk.

The change in potential energy of the ball will be converted into rotational kinetic energy of the disk and translational kinetic energy of the ball. Since the moment of inertia of the solid disk is less than the hollow disk, less energy is required to rotate the solid disk. Therefore, more energy can be converted into translational kinetic energy of the ball attached to the solid disk. Since the balls fall the same distance, the change in potential energy is the same for both systems. Therefore, ball A will have more kinetic energy because it is attached to the solid disk.