What Is a Pendulum Used for?

Throughout history, the pendulum has been a crucial device for essential tasks, such as timekeeping and measurement. Since its discovery in 1602, the pendulum has undergone a series of transformations that have seen it in use ranging from the common household to the standards of nations.

Definition

A pendulum is a weight suspended from a fixed point where gravity and momentum let it swing back and forth.

How It Works

When a pendulum is disrupted from its resting equilibrium state, gravity pulls it down toward its original position. As it falls, it gains momentum; so when it reaches its starting position, it continues to move, rising on the other side. In a frictionless environment, a pendulum would never return to its resting equilibrium state; however, in the real world, a pendulum runs into air drag and friction that eventually slows its velocity.

Timekeeping

Since its discovery in 1602 and until the 1930s, the pendulum clock has been used as the standard for timekeeping. The quartz clock primarily replaced the pendulum clock in the mid 20th century as the most commonly used clock.

Length

For 200 years the pendulum was used as a standard measurement of length. Since gravity is constant at a certain point on Earth, the time it takes for a pendulum to complete its swing from one side to the other would be determined only by its length; hence, many countries used it as their standard measurement of length. After the discovery that gravity varies in certain locations on Earth, the standard was changed. That, coupled with the fact that not all pendulums could be constructed exactly alike and that they would deteriorate over time, resulted in the pendulum being removed as the standard of length.

Gravity

Because a pendulum relies on gravity to make a full swing, called a period, it was used to measure the local acceleration of gravity at a certain location on Earth. This was commonly achieved by comparing the difference of length between a local pendulum's period and that of a standard pendulum clock.

Metronome

A metronome is an inverted pendulum that is used to keep tempo in music. It is essentially an upside-down pendulum rod with weights attached to both ends. The weight at the top determines the tempo as gravity pulls it down, while the weight at the bottom counters the top weight, ensuring the movement. This device is also called a double-weighted pendulum.