Hi all
Why is 500lb of pressure over a short period of time. Such as a few seconds, so much less damaging than 500lb of pressure instantly/impact
Can someone explain
In: 0
Some dynamics can be affected by the rate of change of the force. For instance, our bodies can adapt to quite large forces, but we need time to orient and flex the appropriate muscles, so you can experience something like whiplash if the force changes very quickly and your body is not prepared to absorb the load. This typically applies to systems that are adaptive like animals or machines.
However, I suspect that what you’re asking about is why a 500lb object sitting on something is less damaging than a 500lb object falling on something. The answer to that is that the 500lb object coming to a stop applies much more than 500 lbs of force. It will be 500lb *plus* the force necessary to stop the object, which can be a little bit more, or many times as much, depending on how fast the object was moving and how quickly it comes to a stop.
The amount of damage done in this case will depend on how gradually your surface can bring the object to a halt, and how it absorbs all that energy as it’s being delivered. In the best case you have something like a trampoline or net, which can slow the object down over a long distance, using only a small amount of extra force, and is made of highly elastic material that can handle the extra energy. In the worst case you have a rigid surface that tries to slow down the 500lb mass all at once, experiencing hundreds to thousands of lbs of force and shattering or deforming because it is not elastic enough to store all that extra energy.
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