A tennis player hits a 58.0 {/rm g} tennis ball so that it goes straight up and reaches a maximum height of 7.35 {/rm m}. How much work does gravity do on the ball on the way up?

The answer is - 4.18 J

A work (W) is a product of a force (F) and a distance (d) : W = - F · d (negative because it goes way up, against the gravitation)

Since the force is a product of mass and acceleration: F = m · a

then work would be: W = - m · a · h

It is known:

m = 58 g = 0.058 kg

h = 7.35 m

a = 9.8 m/s² (gravitational acceleration, since is expected that on some height gravitation force will work).

Therefore,

W = - 0.058 * 7.35 * 9.8 = - 4.18 J