A pendulum is a device made of a weight suspended from a pivot so that it can swing freely. It is a simple harmonic oscillator that is used to regulate the movement of clocks and measure the acceleration of gravity in geophysical surveys. A simple pendulum consists of a bob suspended at the end of a thread that is so light as to be considered massless. The period of a simple pendulum is influenced by the position of the pendulum in relation to Earth, and it can be made longer by increasing its length. The period of a simple pendulum is given by the formula T=2π√(L/g), where L is the length of the string and g is the acceleration due to gravity.

There are various other kinds of pendulums, such as the compound pendulum, which has an extended mass like a swinging bar and is free to oscillate about a horizontal axis. A special reversible compound pendulum called Kater’s pendulum is designed to measure the value of g, the acceleration of gravity. A spherical pendulum is one that is suspended from a pivot mounting, which enables it to swing in any of an infinite number of vertical planes through the point of suspension.

A pendulum is subject to a restoring force due to gravity that will accelerate it when it is displaced sideways from its resting, equilibrium position. The restoring force is directly proportional to the displacement, and the simple pendulum is a simple harmonic oscillator for angles less than about 15º. The motion of a pendulum is periodic, and the math is almost.