Key Ideas
1Oscillatory Motion. Motion that repeats itself over and over around a central equilibrium (rest) position, such as a mass on a spring or a swinging pendulum.
2Period and Frequency. Period (T) is the time for one complete oscillation; frequency (f) is the number of oscillations per second, related by f = 1/T.
3Amplitude. The maximum displacement from the equilibrium position during an oscillation.
4Restoring Force. A force that always points back toward the equilibrium position, which is what causes and sustains oscillatory motion.
5Damping. The gradual loss of energy (and amplitude) in a real oscillating system, usually due to friction or air resistance, eventually bringing the motion to rest.
Worked Examples
A pendulum completes one full swing every 2 seconds. Find its frequency.
0.5 Hz
A mass on a spring oscillates with frequency 5 Hz. Find its period.
0.2 seconds
Why does a swinging pendulum eventually stop, even though ideal oscillatory motion would continue forever?
Damping (energy loss from friction and air resistance) gradually reduces the amplitude to zero