ETYM New Lat., from Latin pendulus hanging, swinging. Related to Pendulous.
An apparatus consisting of an object mounted so that it swings freely under the influence of gravity.
Weight (called a “bob”) swinging at the end of a rod or cord. The regularity of a pendulum’s swing was used in making the first really accurate clocks in the 17th century. Pendulums can be used for measuring the acceleration due to gravity (an important constant in physics), and in prospecting for oils and minerals.
Specialized pendulums are used to measure velocities (ballistic pendulum) and to demonstrate the Earth's rotation (Foucault's pendulum).