Explanation:

By the phenomenan of oscillation we can conclude this one as our answer.We can understand it further by understanding mechanism of simple pendulum.

A simple pendulum consists of a mass m hanging from a string of length L and fixed at a pivot point P. When displaced to an initial angle and released, the pendulum will swing back and forth with periodic motion. By applying Newton's secont daw for rotational systems, the equation of motion for the pendulum may be obtained

,
and rearranged as

.