Damping

In an undamped oscillation, energy is only moved back and forth between the two forms of energy involved. In the example of the pendulum, the energy circulates between kinetic energy and potential energy.

All effects that irretrievably convert energy from the oscillation into another form damp the oscillation. If, for example, kinetic energy is converted into heat by friction, the energy in the system decreases. If something is plastically deformed or light is produced, energy is also withdrawn from the system.

Let us imagine a real swinging pendulum that gives off energy to its surroundings through friction. Because energy is withdrawn from the system with every movement, the potential energy soon no longer suffices for the end positions that were still possible at the very beginning of the oscillation. The speed of the motion also decreases. The peak value of the sine of a damped oscillation decreases over time. The waveform, however, remains approximately sinusoidal.

The mathematics of damping is covered later.