(a) Distance travelled by the stone while falling from the height 20 m to the ground = 20 m
The initial velocity of the stone = 0
Acceleration of the stone = g
By using the second equation of motion, we can write,
Here, u = 0, s = 20 m, and 't' is the time taken by the stone to reach the ground.
So,
(b) Using the first equation of motion, we can write, (Where 'v' is the speed of the stone when it hits the ground)
So,