Define a simple pendulum and the length of the pendulum.

(N/A) simple pendulum is defined as an idealized system consisting of a heavy point mass (called a bob) suspended from a rigid support by a massless,inextensible,and perfectly flexible string.
When the bob is displaced from its equilibrium position and released,it undergoes periodic motion.
The length of the pendulum,denoted by $L$,is defined as the distance from the point of suspension to the center of gravity of the bob.