Define simple harmonic motion $(SHM)$.

(N/A) Simple harmonic motion $(SHM)$ is a special type of periodic motion where the restoring force acting on a particle is directly proportional to its displacement from the mean position and is always directed towards the mean position.
Mathematically,it is expressed as $F = -kx$,where $F$ is the restoring force,$x$ is the displacement from the equilibrium position,and $k$ is the force constant.
In $SHM$,the acceleration of the particle is also proportional to its displacement and is given by $a = -\omega^2 x$,where $\omega$ is the angular frequency.