Question

An object takes 5s to reach the ground from a height of 5th on a planet . What is the value of g on the planet ?

Answer 1

Time taken, t = 5 seconds

Displacement, s = 5 metres

Initial velocity, u = 0 metres/second

Let the acceleration be a m/s2m/s2.

When the acceleration is constant, initial velocity, acceleration, time taken and displacement are related by a simple formula:

s=ut+(1/2)at2s=ut+(1/2)at2

Therefore,

5=(0)(5)+(1/2)(a)(52)5=(0)(5)+(1/2)(a)(52)

a×(25/2)=5a×(25/2)=5

a=5/(25/2)a=5/(25/2)

a=10/25a=10/25

a=2/5a=2/5

a=0.4a=0.4

Therefore, the acceleration is 0.4m/s20.4m/s2.

This is the acceleration due to gravity on that planet.

Please note that you can't call ‘acceleration due to gravity’ as ‘gravity’.

Gravity refers to gravitational force. Gravitational force (gravity) due to the planet on any mass ‘m’ (expressed in kilograms) = (0.4×m)(0.4×m) newtons.