Why do soldiers march disorderly while crossing a bridge?

A. To prevent resonance on the bridge
B. To set the bridge into resonance
C. To make the bridge collapse
D. To spread their weight evenly on the bridge

Correct Answer:

Option A – To prevent resonance on the bridge

Explanation

Soldiers march disorderly while crossing a bridge to prevent resonance because when soldiers march in orderly manner across a bridge, they generate a rhythmic oscillation of wave on the bridge and at a certain point, would start oscillation to the same rhythm as that of the marching steps. This oscillation would reach a maximum peak when the bridge can no longer sustain its own strength and hence collapses. So for this reasons, soldier is ordered to march disorderly while crossing a bridge