Question

Why the motion of a simple pendulum considered simple harmonic even though it does not occur in a straight line?

Answer 1

Simple pendulum

A device in which a string is suspended with the help of rigid support with a point mass attached at the end of that string.

Simple harmonic motion

1. When a pendulum moves back and forth through a central position such that the displacement on either side is the same.
2. The restoring force directs the body towards the equilibrium position.
3. An object is a simple harmonic oscillator when the restoring force is directly proportional to displacement.
4. The motion does not need to be straight for it to be in SHM.

The reason the motion of a simple pendulum is considered a simple harmonic motion is because

1. A simple pendulum performs a single oscillatory motion.
2. It moves back and forth from its mean position with the same displacement on both sides just as in simple harmonic motion.