Question

a tennis ball is hit vertically upwards with a velocity of 20m/s. calculate it's retardation as it moves up and the maximum height of the ball

Answer 1

Retardation:

$$a=-g=-9.8\frac{m}{s^2}$$

The maximum height of the ball:

$$h=\frac{v^2}{2g}=\frac{20^2}{2(9.8)}=20\ m$$