 Oscillator

An oscillator is a system capable of repeated motion or variation about a central state. A mass $m$ on an ideal spring with spring constant $k$ satisfiesThe restoring force accelerates the mass toward zero displacement; inertia carries it through that point, producing simple harmonic motion. The kinetic energy is largest at zero displacement, and the elastic potential energy is largest at the turning points.

Real oscillators can include damping, external driving and anharmonicity. A damped harmonic oscillator distinguishes the free transient from the forced periodic response, and a coupled oscillator adds exchange of energy with another dynamical coordinate. This makes an oscillator useful both as a physical device and as an approximation to small disturbances of much more complicated systems.