Damping is the loss of energy from an oscillating system

Forced Vibrations & Resonance — AQA A-Level Physics

Key Definition

Damping — The reduction in energy and amplitude of oscillations due to resistive forces acting on the oscillating system.

Resistive forces (friction, air resistanceThe opposition to currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A). flow. The ratio of potential difference to currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A).. Measured in ohms (Ω).) act in the opposite direction to the velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹..
These forces remove energyThe capacity to do work. Measured in joules (J). from the system, causing the amplitudeThe maximum displacement of a point on a wave from its equilibrium (rest) position. Measured in metres (m). to decrease over time.
DampingThe reduction in amplitude (and energyThe capacity to do work. Measured in joules (J).) of an oscillation over time due to resistive forces such as friction or air resistance. continues until the oscillator comes to rest at the equilibriumAn object is in equilibrium when the resultant force on it is zero. The object is either stationary or moving at constant velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹.. position.
The frequencyThe number of complete oscillations passing a point per unit time. Measured in hertz (Hz). of damped oscillations does not change as the amplitudeThe maximum displacement of a point on a wave from its equilibrium (rest) position. Measured in metres (m). decreases. Only the amplitudeThe maximum displacement of a point on a wave from its equilibrium (rest) position. Measured in metres (m). drops.

Examiner Tips and Tricks

Do not confuse resistive force (opposes motion, causes dampingThe reduction in amplitude (and energyThe capacity to do work. Measured in joules (J).) of an oscillation over time due to resistive forces such as friction or air resistance.) with restoring force (returns oscillator to equilibriumAn object is in equilibrium when the resultant force on it is zero. The object is either stationary or moving at constant velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹.., causes the oscillation).
They do different jobs.