A suspension footbridge once experienced dangerously large oscillations when a troop…
PHYSICS · Subjective · A Level · Physics · Further mechanics and thermal physics · Further mechanics and thermal physics
Problem
A suspension footbridge once experienced dangerously large oscillations when a troop of soldiers marched across it in step.
(i) Explain how a small periodic lateral force exerted by the marching soldiers can lead to large oscillations of the bridge.
(ii) Describe the role of damping present in the bridge structure and surrounding air in limiting the amplitude of these oscillations.
(iii) Suggest two engineering measures that can be taken to reduce the oscillations and explain, using appropriate physical reasoning, how each measure works.