A motion repeating itself is referred to as periodic or oscillatory motion. An object in such motion oscillates about an equilibrium position due to a restoring force

or torque. ... This motion is important to study many phenomena including electromagnetic waves, alternating current circuits, and molecules.

Why does oscillatory motion occur?

This motion takes place when the restoring force acting on the system is directly proportional to its displacement from its equilibrium position. In practice, oscillatory motion eventually comes to rest due to damping or frictional forces.

Why do objects oscillate?

The restoring force acts upon the vibrating object to move it back to its original equilibrium position. ... But an object in vibrational motion wiggles about a fixed position - its original equilibrium position. Because of the restoring force, vibrating objects do the back and forth.