MYP Physics · 10 · extended response
Damping a resonant footbridge panel
Sound and oscillation · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- discriminating
- Marks
- 8
- Topics
- 2
- Answer
- Complete
A lightweight footbridge panel is driven by repeated footsteps. Its undamped vibration amplitude peaks at 6.0 mm near 2.0 Hz. Engineers test two add-on dampers at the same forcing amplitude.
| Driving frequency / Hz | Damper P amplitude / mm | Damper Q amplitude / mm |
|---|---|---|
| 1.5 | 1.5 | 1.2 |
| 2.0 | 2.8 | 1.6 |
| 2.5 | 1.7 | 1.3 |
- a
Interpret Explain why the undamped panel has its greatest response near 2.0 Hz.
2 marks - b
Compare Compare P and Q quantitatively at the resonant frequency.
2 marks - c
Evaluate Recommend a damper for the bridge and specify additional evidence required before installation.
4 marks
Ready to self-mark?Reveal the detailed answer guide
a
Interpret Explain why the undamped panel has its greatest response near 2.0 Hz.
Build a chain of claim, evidence and physics reasoning. Address more than one relevant factor, identify a limitation or assumption, and finish with a conclusion that is conditional on the evidence rather than absolute.
- 1
Identifies 2.0 Hz as close to a natural frequency of the panel.
- 2
Explains that repeated driving near the natural frequency transfers energy effectively, producing resonance and large amplitude.
b
Compare Compare P and Q quantitatively at the resonant frequency.
Build a chain of claim, evidence and physics reasoning. Address more than one relevant factor, identify a limitation or assumption, and finish with a conclusion that is conditional on the evidence rather than absolute.
- 1
Reads amplitudes 2.8 mm for P and 1.6 mm for Q at 2.0 Hz.
- 2
States that Q reduces amplitude by a further 1.2 mm relative to P, or that Q's amplitude is about 43% lower than P's.
c
Evaluate Recommend a damper for the bridge and specify additional evidence required before installation.
Build a chain of claim, evidence and physics reasoning. Address more than one relevant factor, identify a limitation or assumption, and finish with a conclusion that is conditional on the evidence rather than absolute.
- 1
Recommends Q if vibration reduction is the main priority, supported by its lower amplitude at all tested frequencies, or gives another defensible conditional recommendation.
- 2
Recognises that measurements at only three frequencies may miss another peak or frequency shift.
- 3
Requests relevant evidence such as a finer frequency sweep, transient response, performance under varied crowd forcing, added mass, fatigue, weather durability, cost, or maintenance.
- 4
Explains how the requested evidence addresses safety, comfort, or whole-life performance rather than merely asking for more data.
Private on this device