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The most chatters online in one day was 12, 22-09-2008. Nomad |
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Just for Fun Today's QUESTION
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Just thought i'd get some chat going. Why do soldiers break step in marching over a bridge? It's not a joke, but guess it could be made into one. Paddington 
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I thought it was to avoid the possibility of resonant freuency of the bridge being triggered. A good modern example was the millenium bridge on the Thames, the oscillations were increased as people started to sync with the already present oscillations due to poor design. It was a strange experience when I was on it as it was hard not to move in sympathy with it or even stand. Half an hour later the bridge was closed.
The most famous example has to be the Tahoma Bridge incident in the US around 1940. The oscillation was due to wind but the same effect can be achieved if many people are walking in step. Am I right in asuming this? I noticed on Chelsea bridge there is a sign telling troops to break step when crossing. |
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Hi Guys,
Yes Nomad, that's right. With a large number of troops, or people, their combined steps could coincide with the resonant frequency of the bridge, causing it to sway, and eventually collapse! See here, the Tacoma bridge {Edit...} Hmmm, my Youtube input didn't work, so here is the link instead! Okay, it didn't, but putting the link in seems to do the same thing! I give up! This was caused by the wind, but the principle is just the same. Basically, resonance is the production of maximum amplitude by a short, minimum force. There! Physics lessons do have some use!  Hope that helped, James CP Officer, and now Physics enthusiast! My teacher would be so proud! Last edited by james_allen; 07-01-2008 at 07:12 PM. |
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Learn next?
Umm...the moon isn't actually made of cheese! Or so my little nephew informs me! |
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Well done Everyone !
I'll be handing out chocolates next term. To avoid stressing the bridge excessively... if they march in step, there's a chance that their steps will coincide with the resonant frequency of the bridge and cause possibly dangerous amplified shaking of the whole structure And anyone who's ever heard the sound of 100 boots or more marching - that sound can stir the skin and it's resonation create a huge emotional response. |
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