# Thread: how much momentum does it take to harm a person?

1. Hi,
i'm trying to estimate when does a hit of a vorex ring can cause you some damage.

if we say that the whole momentum is passed to a person at once, how much momentum would couse injur

2.

3. Originally Posted by guytsur7
Hi,
i'm trying to estimate when does a hit of a vorex ring can cause you some damage.

if we say that the whole momentum is passed to a person at once, how much momentum would couse injur
What is a vorex ring?

There is no set amount of momentum that would cause injury. It all depends on the time over which the momentum is transferred, the organs to which the momentum is transferred, the area of the body which absorbs the momentum, etc., etc. For example, your automobile accelerates you to cruising speed, transferring some momentum to you without any damage. Then you crash into a brick wall, transferring the same momentum in the opposite direction, and that will kill you.

4. This is a good example for a vortex ring gun: Giant Vortex Cannon - YouTube

i don't need an exact number just some number to start with and get a feeling about things hat's all.
i can assume that the hit is fast enough in order to say that all the momentu, is transferd in infinite time (some sort of delta function).

so let's say if it's hit you in the head how much wold it take tocause serious damage?

5. Kinetic Energy is what kills, not so much momentum. Mathematically, the difference is that momentum is (mass times velocity) and kinetic energy is . It's important because you can see that for kinetic energy, velocity is much much more important than mass. That's why tiny bullets are so much more deadly than comparatively large arrows.

Looking at the video, it looks like the destructive force was minimal. The brick structure fell over because the vortex had enough momentum to push it gently over. Pushing a person gently, even with an infinite amount of force, will not kill them, just move them.

6. its not momentum that hurts, its the over pressure. for instance an overpressure of .5 psi will crush you rib cage
thats how a blast wave kills without the shrapnel

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