XD Talk

Captain Jack · 10-13-2007, 02:12 AM

Hello everyone. I was hoping you can help me out in helping out a friend on another forum. His question is this:

Quote:

I'm writing a response letter to someone in my English class right now, and he wrote about a guy who buried his wife's cat alive and the wife shot him. Anyway, he said "The force of [the bullet] knocked me over."

So I remembered when the Mythbusters tested this, and I thought they had found that it was more the shock and sudden loss of awareness of being shot rather than actual force of the bullet that knocks people over. However, I just tried to calculate it out, assuming low numbers, that the bullet is going about 800 m/s, the mass is .003 kg, and the distance was 2 meters. I'm thinking that actually is enough force to knock someone over.

Are the Mythbusters wrong? Do I not remember that episode correctly? Do I suck at math? And what should I tell this kid in the response letter?

I feel that you all may know better than I do, and could provide some data to help him out.

Thanks in advance. I really appreaciate it.

**XDAndMe** · 10-13-2007, 02:29 AM

I'm going to go out on a limb here and preemptively say, without any calculations, that theoretically a bullet does have enough energy to knock over a person but in practice it won't usually happen if the bullet works the way it is supposed to. Handgun cartridges can generate several hundred ft-lbs of energy at the muzzle, which I would think is sufficient force to at least push an average sized person by some amount. However, a bullet works by causing a disturbance to internal organs and tissue (leading to tissue damage and blood loss, etc.) If all of the bullet's energy went into pushing the person or knocking him back, I would suspect that it would not do a good job of disturbing vital tissue. Therefore, I think it is safe to say that most of a bullet's energy goes into disrupting tissue rather than knocking the person down. I'm sure a fair amount of energy is lost in "pushing," and that it is possible for someone to be knocked down, but I think most of the time the person will just fall after enough tissue/nerve damage or loss of blood or blood pressure.

So in short, I don't think bullets will knock people down in most situations. If we were made of steel or some other material that doesn't disrupt like tissue (or even ballistic gelatin) does, then yes... most of the energy would go into pushing us back or knocking us down. However due to the nature of tissue and how it absorbs and transfers energy, I have to call the BS flag on this story.

My theory is a little different if you're talking about 1oz. lead slugs from a 12-ga. shotgun

gsh341 · 10-13-2007, 02:30 AM

Newtonian physics is your friend in this debate.

Newton's Third Law states that for every action there is an equal and opposite reaction.

Thus, if the force of the bullet striking someone were enough to knock them over, then the shooter must be knocked over too, unless the weapon is mounted or otherwise fixed.

So, everything from a .22LR to a 12ga slug/00 Buck will not knock the average adult down. An anorexic midget maybe,

but not the average adult.

However, a large enough round (i.e. 20mm cannon) would knock a person over. That would be redundant though, as the person would also be completely blown apart.

Magzilla · 10-13-2007, 02:35 AM

Here is an cut out from .pdf file that another forum member sent me on the subject of Handgun Wounding Factors and Effectiveness. It kinda addresses your question.

**XDAndMe** · 10-13-2007, 02:38 AM

Quote:

Originally Posted by gsh341

Newtonian physics is your friend in this debate.

Only one problem with that... you're assuming ideal conditions where the "receiver" is just as prepared for the force of the bullet as the shooter is for recoil. Someone shooting a shotgun slug will be standing accordingly and properly supported for the recoil, not to mention the aid of recoil absorbers in the weapon itself. Someone being shot at may not be anticipating a lead slug hitting him.

Magzilla · 10-13-2007, 02:40 AM

Here is the whole .pdf file here!

http://webpages.charter.net/riffmong...ectiveness.pdf

gsh341 · 10-13-2007, 02:48 AM

You can also do the math to find out what the perceived force of a bullet striking the body would be.

You can fit 320 .45ACP bullets into 1 sq/ft.

A .45ACP generated about 450 ft/lbs of energy.

So, 450 ft/lbs / 320 = 1.4 lbs of perceived force.

Someone check my math and logic, but I believe this is correct.

I really don't think you can get knocked over by 1.4 lbs.

**XDAndMe** · 10-13-2007, 02:50 AM

This might do the trick

http://pl.youtube.com/watch?v=-EVqT3XEzss

Captain Jack · 10-13-2007, 03:17 AM

Thank you all for your help. That should be more than enough to help him out.

**Rustynuts** · 10-13-2007, 06:08 AM

Quote:

Originally Posted by gsh341

You can also do the math to find out what the perceived force of a bullet striking the body would be.

You can fit 320 .45ACP bullets into 1 sq/ft.

A .45ACP generated about 450 ft/lbs of energy.

So, 450 ft/lbs / 320 = 1.4 lbs of perceived force.

Someone check my math and logic, but I believe this is correct.

I really don't think you can get knocked over by 1.4 lbs.

I think your math is wonky. First off it's FT-LBs, not FT/LBS. Then you seem to be mixing a SQUARE foot into the singular ft-lb "equation". Not sure how to fix it, if you even can!