Question

What is the necessary condition for a periodic motion to be classified as a

simple harmonic motion?

Answer 1

The restoring force must be proportional to the displacement and act opposite to the direction of the motion. We can write the necessary condition for a periodic motion to be classified as SHM as follows:

$$F=-kx,$$

here, $F$ is the restoring force, $x$ is the displacement from the equilibrium position and $k$ is the spring constant.