# A car suspension system uses springs and shock absorbers (dampers) to reduce the vibrations felt by passengers when driving over bumps. Without the dampers, the suspension would undergo free oscillations after hitting a bump. Explain how the dampers reduce the amplitude of these oscillations and why engineers choose a level of damping that allows the car body to return to its rest position as quickly as possible without oscillating.

> AQA A-Level Physics (7408) — 3.6.1 Periodic Motion · Explain · 5 marks

> Without dampers, a car suspension spring would continue to oscillate for many cycles after hitting a single bump in the road.

## Mark scheme (5 marks)

1. The dampers remove/transfer energy from the oscillating system (accept: do work against a resistive/friction force)
2. Each successive oscillation has a smaller amplitude because energy has been removed (amplitude decreases over time)
3. The natural frequency of the suspension is the frequency at which it would oscillate freely / without damping
4. The chosen level of damping is critical / heavy damping means the system returns to equilibrium slowly whereas light damping means many oscillations occur before returning to equilibrium (credit: identifying the need to avoid resonance / excessive oscillation)
5. The optimum (critical) damping returns the system to equilibrium in the shortest time without oscillating / a compromise between light and heavy damping is chosen

## Key terms

- [damping](https://www.gradenine.co.uk/glossary/damping)
- [amplitude](https://www.gradenine.co.uk/glossary/amplitude)
- [free oscillation](https://www.gradenine.co.uk/glossary/free-oscillation)

## Related

- [Revision notes for AQA A-Level Physics (7408)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-car-suspension-system-uses-springs-66607dc4) · Published by Druglandscape Ltd.