Question

5. Solve the following examples.
An object takes 5 s to reach the grond
from a height of 5 m on a planet.
What is the value of g on the planet?
​

Answer 1

Given :

➳ Time taken by object to reach at the ground = 5s

➳ Height = 5m

To Find :

⟶ Acc. due to gravity of planet.

Solution :

➠ Acceleration due to gravity continuously acts in downward direction.

➠ For free falling object, g is taken positive.

➠ We can easily solve this question by using second equation of kinematics.

➠ For free falling object, u = 0

$\longrightarrow\tt\:H=ut+\dfrac{1}{2}gt^2\\ \\ \longrightarrow\tt\:H=(0\times t)+\dfrac{1}{2}gt^2\\ \\ \longrightarrow\tt\:5=\dfrac{1}{2}g(5)^2\\ \\ \longrightarrow\tt\:10=25g\\ \\ \longrightarrow\boxed{\bf{g=0.4\:ms^{-2}}}$

Answer 2

★Answer:–

• Time taken, t = 5 seconds

• Displacement, s = 5 metres

• Initial velocity, u = 0 metres/second

Let the acceleration be a m/s2 .

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

s=ut+(1/2)at2

Therefore,

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

g×(25/2)=5

g=5/(25/2)

g=10/25

g=2/5

g=0.4

Therefore, the acceleration due to gravity is 0.4m/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) newtons.