A simple pendulum of length 100 cm performs S.H.M. Find the restoring force acting on its bob of mass 50 g when the displacement from the mean position is 3 cm.

As per the given question,

we can list out the given quantity

Length L = 100 cm = 1m,

mass m = 50 g = 50 x $10^{-3}$ kg

displacement x = 3 cm = 0.03m ,

g = 9.8 m/$s^2$

To find = Restoring force, F = ?

Solution –

Restoring force, F =mg sin θ = mgθ

(Since for small angle θ, sin θ = θ)

F = mg x $\frac{x}{L}$

F = 5 × $10^{-2}$ x 9.8 x 0.03

F = 1.47 × $10^{-2}$ N