Answer
a. As far as vertical motion is concerned, the tennis ball starts from rest, and drops y meters. Relate the height dropped to the time.
$$y = \frac{1}{2}g t^{2}$$
$$ t = \sqrt{\frac{2 y}{g}}$$
This is discussed on page 48.
The horizontal velocity of the tennis ball does not change. At maximum speed, the horizontal distance it moves is d.
$$d = vt = (v)\sqrt{\frac{2 y}{g}} $$
Solve for the maximum speed.
$$v = \frac{d}{t} = \frac{d}{\sqrt{\frac{2 y}{g}}} $$
b. Plug the numbers given into the equation just derived to arrive at v = 26.8 m/s.
c. No. The ball is in free fall and the acceleration is independent of mass.
