Question

a tennis ball is hit vertically upwards with a velocity of 20m/s. what is it's Decelaration as it moves upward? calculate the maximum height reached by the ball.

Answer 1

-9.81 m/s^2

0 = 20 - 9.81 t

then

h = 20 t - 4.9 t^2

or
(1/2) m v^2 = m g h
so
h = v^2/2g