Question

An iron ball of mass 5 kg is released from a height of 125 m and falls freely to the ground. Assuming that the value of g is 10 m/s2, calculate time taken by the ball to reach the ground.

Answer 1

An iron ball of mass (m) = 5 kg

Distance travelled by the ball (s) = 125 m

Initial Velocity of the ball (u) = 0 m/s

Acceleration (g) = 10 m/s²

Newton’s second equation of motion gives,

`s = ut + 1/2 at^2`

`125 = 0 xx t +1/2 xx 10 xx t^2`

125 = 5t²

`t^2 = 125/5`

t² = 25

t = `sqrt25`

t = 5 s

The ball takes 5 seconds to reach the ground.