A platoon of soldiers marches in step along a road. Why are they ordered to break step when crossing a bridge?

Answer 1

Check this site: this is what would happen if resonance builds up. In this case it was considered to be done by the wind which created a small resonance in the bridge which then was self increasing.

Answer 2

There are three types of vibrations especially in solid bodies.

1. Free vibration
2. Forced vibration
3. Resonant vibration.

If a body is set it into vibration and left free (no more external force) then the body will vibrate with a frequency called NATURAL FREQUENCY. Every object has more than one number of natural frequencies.


If a vibrating force A is applied on a body, say B, then the body B will vibrate with the frequency of A. It will not vibrate with its natural frequency. This is forced vibration.

If in forced vibration, the natural frequency of B coincides with that of A then the vibration is called resonance and the amplitude of vibration becomes very high.

If the vibrating force applied by the soldiers happened to be equal to the natural frequency of the bridge, the amplitude of vibration may become enough to collapse the bridge.

Answer 3

If the troops march in uniform rhythm across the bridge, it will cause the bridge undulate, that is move like a wave up and down. If it isn't made very well, the waves will add to one another, making the waves stronger and more likely for the bridge to topple. The break step by the soldiers is in effort to avoid such a catastrophe.

Answer 4

The stepping of marching soldiers is in sync and can cause the bridge to vibrate at its resonant frequency. If the bridge vibrates at this frequency, serious damage can be done to it.

Answer 5

Because if they would keep going like that, the oscillations provoked by their marching would be quite dangerous. But if they break step, the oscillation provoked by each soldier in part would interfere with the oscillations of other soldiers and they would interfere with each other and the oscilation of the bridge would be smaller

Answer 6

You must be knowing resonance frequency..Every molecular made object has its own lattice structure.

Especially solids stck to the nature of rigidity..

At their resonance frequency if the molecules would have vibrational motion..But they are rigid.

To convert the energy obtained by vibration they tend to change the vibration energy to trasilational energy..

As its resonance frequency is reached all the energy coming from vibration is just enough to escape the molecules from its lattice compact placements.

It causes the collapse and finally leading to the cracking or destruction.

Answer 7

I do not have a concrete answer, but I would guess that this is done in order to keep an enemy from discerning, say, civilians from soldiers by merely sound, as bridges are common control points and can be rigged to collapse fairly easily.

Answer 8

because alot of footpath roads that they are going to march over cant support the weight of all those people marching next to eachother, so by breaking step they decrease the stress on the bridge
also, a little morbidly, if only one or two go on out front and theres a mine or booby trap, and it is set off, then less people will die :)

Answer 9

BECAUSE MR NAIVE.IF THEY DONT BREAK THEIR STEPS,THAN THE BRIDGE WOULD BE IN RESONANT MOTION
VIBRATING PRETTY QUITE DAMN BADLY-BECUASE OF THE RYTHMIC STEPS OF THE MARCHERS,THAT WOULD SET THE BRIDGE TO CREATE RESONANCE AND THUS WHICH MAY RRESULT IN THE BRIDGE GETTING COLLAPSED

Answer 10

if it is a hanging bridge....thay sways...it is to supposedly keep the bridge from collapsing.....but discovery channel mythbusters proved to be untrue I believe.