Harmonic oscillator
. Here is a positive constant. If it is the only force acting on the system, this vibrator is called a simple harmonic oscillator. The motion of this system shows a sinusoidal vibration with constant amplitude and frequency. If there is a frictional force proportional to the speed, this oscillator is called a damped oscillator. In this case, the frequency is smaller than that without friction, and the amplitude also decreases gradually with time. Finally, when an external force other than frictional force acts on this system, this oscillator is called a forced oscillator. Epidemiological examples of such vibrators include acoustic systems such as springs with massed objects, small oscillating pendulums, and other strings. There are also electrical harmonic oscillators, such as RLC circuits, that show similar behavior.