Question

A body is dropped from a height of 80 m freely under gravity. Find the time taken by body to reach ground.
(g = 10 ms–2)

Answer 1

The ball reaches the ground in 4 seconds.

Explanation:

Given Height, s = 80 m

Since the body is falling freely, it is under uniform acceleration due to gravity, g =  appx. 10 ms-2

Applying the equation of motion, we get s =  ut + 1/2at2, where t is the time taken to reach the ground.

u = 0 m/s as body is at rest.

a = g = 10 m/s2

We get: 80 = 0*t + 1/2*10*t2

80 = 5t2

t2 = 80 / 5 = 16

So t = root of 16 = 4 seconds.