(a) Two spheres of equal mass and radius are rolling across the floor with the same speed. Sphere 1 is a uniform solid; sphere 2 is hollow. Is the work required to stop sphere 1 greater than, less than, or equal to the work required to stop sphere 2?

(b) Choose the best explanation from among the following:

I. Sphere 2 has the greater moment of inertia and hence the greater rotational kinetic energy.

II. The spheres have equal mass and speed; therefore, they have the same kinetic energy.

III. The hollow sphere has less kinetic energy.