Simple Pendulum

Q.4.  What is a simple pendulum, Explain the motion of the bob is simple harmonic motion

Ans.   Simple Pendulum

A simple pendulum consists of a bob of small size and of large density. It is suspended from a rigid support so that is can vibrate freely. The suspended string must be of very small density and un-extendable.

In the equilibrium position O, the net force is zero and the bob is stationary. Now it is brought to position A, On releasing it moves towards the mean position O under the restoring force.


Force acting on a displaced pendulum, The restoring force that cause the pendulum to undergo simple harmonic motion is the component of gravitational force mg sing0 tangent to path of motion








i.  At the mean position it again maximum velocity so its kinetic energy and momentum will be maximum. It will o up to other extreme position B due to inertia

ii.  At B it has zero velocity so kinetic energy is zero bu the potential energy is maximum

iii.  Again it will move towards mean position O gains maximum kinetic energy and momentum at O and moves up to the extreme position A due to inertia

iv.  At any displacement from mean position it has partially kinetic energy and partially potential energy but sum of these energies is constant.

In this way it will oscillate between the extreme positions A and B about the mean position O.