C.4.6—Types of damping

Classify the response

Light damping lets the system oscillate about equilibrium while its amplitude decreases gradually. Critical damping returns the system to equilibrium in the shortest time without oscillating. Heavy damping also avoids oscillation, but returns to equilibrium more slowly than critical damping.

Damping	Crosses equilibrium repeatedly?	Return to equilibrium
Light	Yes, with decreasing amplitude	Oscillatory decay
Critical	No	Fastest possible return without oscillation
Heavy	No	Slower than critical damping

Choose the response from the design goal

A system that must settle quickly without repeated oscillation is adjusted close to critical damping. Too little damping allows repeated crossings of equilibrium; too much damping resists the motion so strongly that the return takes longer.

Common trap

Critical and heavy damping are both non-oscillatory, but they are not equally fast. Critical damping is the fastest return without overshoot; heavy damping is slower.

How it is assessed

Questions identify a displacement-time response, compare energy dissipation or Q, or select the correct qualitative behaviour for a stated damping level.

Command terms

State and explain / Which statement

What earns marks

Distinguish light damping by decaying oscillations, critical damping by the fastest non-oscillatory return, and heavy damping by a slower non-oscillatory return.

Watch for

Calling critical damping the fastest return overall without the “without oscillation” condition, or confusing light damping with no damping.

Representative question

[Maximum number: 1]

Which graph of displacement x against time t represents the motion of a critically damped body?

C.4.6—Types of damping

Compare Types of Damping

C.4.6 Exam Analysis

Assessment in practice

Question 1