Damped Oscillations

This lesson covers: 

  1. How energy is lost from oscillating systems due to damping forces
  2. Different levels of damping and their effects on amplitude
  3. The impact of damping on resonance
  4. Examples of deliberately damping systems

Energy loss in oscillating systems

In practice, any oscillating system loses energy to its surroundings, usually due to frictional damping forces like air resistance. This energy loss causes the amplitude of the oscillations to decrease over time.


Causes of damping

  • Frictional forces
  • Air resistance
  • Internal energy losses


Deliberately damping systems

Many systems are deliberately damped to prevent excessive oscillations or to minimise the effects of resonance:

  • Car suspension systems use shock absorbers to damp oscillations.
  • Moving coil meters have critical damping to prevent needle oscillation.

Different damping levels

The degree of damping can vary:

Light damping

Graph showing light damping with displacement over time.
  • Small damping force reduces the amplitude of oscillation gradually over time.

Critical damping

Graph illustrating critical damping showing displacement over time.
  • Stops oscillations rapidly without oscillating.

Heavy damping

Graph showing the effect of heavy damping on oscillations over time.
  • Reduces the amplitude of oscillations more rapidly than light damping.

Overdamping

Graph showing overdamping with displacement decreasing over time.
  • Critical damping reduces the amplitude to zero gradually without oscillating.


Effect of damping on resonance

Damping a resonating system reduces the amplitude of oscillation.

This results in a flatter amplitude against driving frequency graph.

Graph showing the effect of damping on resonance with amplitude against driving frequency for light and heavy damping.
  • Light damping - Very sharp, tall resonance peak, highly sensitive to driving frequency.
  • Heavy damping - Lower, flatter peak, less sensitive to driving frequency.