3.6.1.4
Heavy damping returns to equilibrium slowly without oscillating
Forced Vibrations & Resonance — AQA A-Level Physics
Key Definition
Heavy damping — Damping where the oscillator returns to equilibrium very slowly without any oscillations.
- No oscillations. DisplacementThe distance moved in a particular direction from a starting point. A vector quantity. Measured in metres (m). does not cross zero.
- The return 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.. takes much longer than the critical 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. case.
- Example: door dampers prevent doors slamming shut by making them close slowly.
Worked Example
A mechanical weighing scale has a needle that oscillates before settling. Which type of 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. should be applied?
Show Solution
1
Consider the requirements
The needle should not oscillate (rules out light 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.). It should settle as quickly as possible (rules out heavy damping).
2
Choose
Critical damping allows the needle to reach its reading in the shortest possible time without overshooting or oscillating.
Answer
Critical damping should be applied.