Question
A ball thrown vertically a upwards with a speed 29.4 m/s from the top of tower reaches the ground in 8s. Find the height of the tower.
Solution
Given, a ball is thrown vertically upwards with a speed 29.4 m/s.
Let, ground be the reference point and vertically upward direction is taken as positive.
We have,
Initial velocity, u = 29.4 m/c
Acceleration due to gravity, a = g= -1m/s2
Time taken for the ball to reach the ground, t = 8s
Initial distance, x = 0
Let, h be the height tower.
Therefore,
Displacement, xo = h
Using the equation of motion, we have
Now 
0 = h + 235.2 - 313.6
h = 78.4m, is the required height of the tower.
