(a) Ball 1 is thrown to the ground with an initial downward speed; ball 2 is dropped to the ground from rest. Assuming the balls have the same mass and are released from the same height, is the change in gravitational potential energy of ball 1 greater than, less than, or equal to the change in gravitational potential energy of ball 2?
(b) Choose the best explanation from among the following:
I. Ball 1 has the greater total energy, and therefore more energy can go into gravitational potential energy.
II. The gravitational potential energy depends only on the mass of the ball and the drop height.
III. All of the initial energy of ball 2 is gravitational potential energy.