A particle or rigid body performs oscillations if it travels to and fro in some way about a central position, usually a point of stable equilibrium. Examples include the swings of a simple or compound pendulum, the bobbing up and down of a particle suspended by a spring, and the vibrations of a violin string. The oscillations are damped when there is a resistive force and forced when there is an applied force. See linear theory of equilibria, simple harmonic motion.