Question

A tennis ball is served horizontally from 2.4m above the ground at 30m/s
a) the net is 12m away and 0.9m high.. Will be ball clear the net?
b) where will the ball land.. ?

Answer 1

The time for the ball to reach the net:
distance = speed x time
t = 12/30
t = 0.4 seconds

a) Height of ball after 0.4 seconds:
h = 2.4 - ut - 1/2 at²; u = 0
h = 2.4 - 1/2 x 9.81 x (0.4)²
h = 1.62 m
h > 0.9 m so the ball will clear the net.

b) The time taken for the ball to hit the ground:
2.4 = 1/2 x 9.8 x t²
t = 0.70 seconds
Distance = speed x time
d = 30 x 0.7
d = 21 m
The ball lands 21 m away.