Can a small arms bullet knock you off your feet?
Discussion
Discussion taken from this thread: http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Can anyone add any definitive opinion on the question of whether a bullet from a handheld gun can knock a person off of their feet through the force alone?
Hmm.. I think it is true. Newton's third law, if the bullet had enough force to knock someone over the recoil would knock the shooter over.Go on...you argue with the retired military explosives guy 
(ahem, recoil = arm moves. don't believe the tv where people fire a clip of 45 with one hand - it's not real...).It is true - Newton's Third Law.
Mythbusters tested it with a pig carcass hanging from a hook where the slightest movement would push the carcass off of the hook. They tried all sorts of calibre weapons from 9mm up to and including shotguns and assault rifles. From memory only one knocked the carcass off and that was due to an anomaly rather than being a true result.
ETA: For real world examples, view the Zapruder film of the JFK assassination - the first shot hit him in the upper back/neck with the bullet travelling down from above to hit him. The shot did not move his body at all.
The more ignorance is "churched up", such as quoting luminaries like Newton, the more humorous that ignorance becomes. Wrap a turd in a Persian rug and it will still stink.It's a bit of both. People might go down, but its not the force "pushing" them over. Not unless they were already off balance. Shock/injury on the other hand might put people down.
Basically a round lacks sufficient kinetic energy to move a person (people being squishy, tend not to stop the round outright with their skin), in general anyway, anorexics and a blunderbuss may have varied results
It may, however, cause other circumstance causing a person to move/drop/die/etc
I'm also sure this has been done to death and thoroughly debunked.
Still not convinced - I seem to recall seeing footage of someone taking a round with a bullet proof vest on and remaining standing.
Can anyone add any definitive opinion on the question of whether a bullet from a handheld gun can knock a person off of their feet through the force alone?
roachcoach said:
Jimbeaux said:
youngsyr said:
tinman0 said:
130R said:
Jimbeaux said:
130R said:
No handgun will knock a human being over
That is untrue.(ahem, recoil = arm moves. don't believe the tv where people fire a clip of 45 with one hand - it's not real...).
Mythbusters tested it with a pig carcass hanging from a hook where the slightest movement would push the carcass off of the hook. They tried all sorts of calibre weapons from 9mm up to and including shotguns and assault rifles. From memory only one knocked the carcass off and that was due to an anomaly rather than being a true result.
ETA: For real world examples, view the Zapruder film of the JFK assassination - the first shot hit him in the upper back/neck with the bullet travelling down from above to hit him. The shot did not move his body at all.
Edited by youngsyr on Monday 23 July 14:16
The more ignorance is "churched up", such as quoting luminaries like Newton, the more humorous that ignorance becomes. Wrap a turd in a Persian rug and it will still stink.Basically a round lacks sufficient kinetic energy to move a person (people being squishy, tend not to stop the round outright with their skin), in general anyway, anorexics and a blunderbuss may have varied results
It may, however, cause other circumstance causing a person to move/drop/die/etcI'm also sure this has been done to death and thoroughly debunked.
Edited by roachcoach on Monday 23 July 14:44
youngsyr said:
fido said:
youngsyr said:
It is true - Newton's Third Law.
Mythbusters tested it with a pig carcass hanging from a hook where the slightest movement would push the carcass off of the hook. They tried all sorts of calibre weapons from 9mm up to and including shotguns and assault rifles. From memory only one knocked the carcass off and that was due to an anomaly rather than being a true result.
ETA: For real world examples, view the Zapruder film of the JFK assassination - the first shot hit him in the upper back/neck with the bullet travelling down from above to hit him. The shot did not move his body at all.
Better to use Conservation of Energy to explain. A pig carcass will absorb most of the energy from a bullet hence very little is left over to move the carcass. The same experiment with a dummy and bullet-proof vest would result in the dummy moving backwards.Mythbusters tested it with a pig carcass hanging from a hook where the slightest movement would push the carcass off of the hook. They tried all sorts of calibre weapons from 9mm up to and including shotguns and assault rifles. From memory only one knocked the carcass off and that was due to an anomaly rather than being a true result.
ETA: For real world examples, view the Zapruder film of the JFK assassination - the first shot hit him in the upper back/neck with the bullet travelling down from above to hit him. The shot did not move his body at all.
roachcoach said:
There's very old footage of a guy on one leg taking a rifle round at point blank range.
Not sure of source/veracity however.
As I say, being shot might make you fall over, but its almost certainly due to events other than, or interacting with the kinetic energy.
The end result is, I guess, the same everywhere but the lab. shoot a dude in a lab braced for it in a vest and there's no way he's going down. Shoot some guy the chest and there's a half dozen reasons he may, or may not go down. All a bit academic really
Not sure of source/veracity however.
As I say, being shot might make you fall over, but its almost certainly due to events other than, or interacting with the kinetic energy.
The end result is, I guess, the same everywhere but the lab. shoot a dude in a lab braced for it in a vest and there's no way he's going down. Shoot some guy the chest and there's a half dozen reasons he may, or may not go down. All a bit academic really
The argument above seem pretty one-sided to me. I can't see a bullet can knock a person over, particularly the way you might see it in Hollywood.
In the real world, a person (from what I have seen on footage, not my own experience thankfully), they tend to collapse suddenly but undramatically like a sack of spuds, not thrown spectacularly backwards like being hit by a car.
In the real world, a person (from what I have seen on footage, not my own experience thankfully), they tend to collapse suddenly but undramatically like a sack of spuds, not thrown spectacularly backwards like being hit by a car.
tinman0 said:
youngsyr said:
Mythbusters tested it with a pig carcass hanging from a hook where the slightest movement would push the carcass off of the hook. They tried all sorts of calibre weapons from 9mm up to and including shotguns and assault rifles. From memory only one knocked the carcass off and that was due to an anomaly rather than being a true result.
Did they put body armor on the pig? Personally speaking, I wouldn't want to take a round from a 45. The idea that he'd be standing or or flat on his back when 45 is bouncing round his interior is quite immaterial, the time he has left to function is quite limited by that point.The "pig test" wouldn't work as it was set up so that even a tiny force would knock the pig off. Don't forget that the recoil on some of these guns is significant and would have knocked the pig off if the gun were attached to a pig firing away from it.
I think I read a hypothesis somewhere that quite a few unexperienced people do knock themselves off their feet because that's what Hollywood has taught them to expect - in an "I'm shot therefore I must be dead" sort of way. Whereas victims who haven't seen film stunts tend to remain on their feet and/or fall in a natural "physics" way.
ninja-lewis said:
I think I read a hypothesis somewhere that quite a few unexperienced people do knock themselves off their feet because that's what Hollywood has taught them to expect - in an "I'm shot therefore I must be dead" sort of way.
You mean inexperienced at being shot...?I can't think that anyone actually being shot is going to wonder how best to fall over.
Lots of videos of guys taking a .357 Mag in the bulletproof vest and not being thrown over, 2nd chance, the BP vest manufacturer, are famous for demonstrating their vests with a "live" demonstration.
A Handgun cartridge such as the 9mmP, .45 ACP or .357 Mag will not have enough energy to knock a person over, a 9mmP, 8 gram bullet travelling at 350 m/s has only 500 J of energy. The king of handgun rounds currently, the .500 S&W, has "only" a 23 gram bullet travelling at 600 m/s for 3kJ worth of energy.
Get hit by a .50 inch Browning (50 gram at 900 M/s for 15kJ of energy) and you will be bounced off your feet, if you survive that is.
A Handgun cartridge such as the 9mmP, .45 ACP or .357 Mag will not have enough energy to knock a person over, a 9mmP, 8 gram bullet travelling at 350 m/s has only 500 J of energy. The king of handgun rounds currently, the .500 S&W, has "only" a 23 gram bullet travelling at 600 m/s for 3kJ worth of energy.
Get hit by a .50 inch Browning (50 gram at 900 M/s for 15kJ of energy) and you will be bounced off your feet, if you survive that is.
Edited by Traveller on Tuesday 24th July 10:20
Use Psychology said:
isn't there a difference between not falling over when you know someone is going to push you, and not falling over when you're not expecting it? This is why people don't fall over when they fire guns - they are braced and expecting the recoil.
Fair point, although a .50 Browning cartridge will turn you into superman, where you expect it or not. Edited by Traveller on Tuesday 24th July 10:41
don4l said:
Getting hit by a 40g bullet travelling at 330 m/s would be like getting hit by a car travelling at 0.015 mph.
That wouldn't knock you over, IMHO.
It would also be the same as getting hit by a bag of sugar that was travelling at 29mph.
Don
--
you have imagine the car stopping dead and transferring all of its momentum to the person - still think you wouldn't fall over? That wouldn't knock you over, IMHO.
It would also be the same as getting hit by a bag of sugar that was travelling at 29mph.
Don
--
I don't much fancy my chances with a 30mph bag of sugar either tbh.
mattnunn said:
I feel the trajectory of the bullet is all important, in a precise horizontal plane any movement of the victim will be horizontal, so rather than lifting you off you're feet it would produce some kind of Michael Jackson moon walk effect.
That does conjure up some funny images, very Naked Gun movies. The bullet will act on the vest in a very short space of time, so not a gentle push, for a Thriller impersonation, but a quick impulse, .25 of a sec for example, to transfer the energy to the bulletproof vest. SHAMON...YEA...I am posting this link to a site that hosts mostly military videos. There are many in the 530+ pages that have the word GRAPHIC in the title. These tend to be people being shot. Not one of them is blown off their feet.
Watch at your own risk.
http://www.military.com/video/shock-and-awe/page/3...
Watch at your own risk.
http://www.military.com/video/shock-and-awe/page/3...
Surely this is can be approximated as a perfectly inelastic collision, this assumes the bullet hits the person and remains stuck in them, rather than bouncing off or going straight through. As such a simple conservation of momentum calculation will give the velocity of a person after being struck by a bullet.
Taking the browning bullet we have a mass of m1 = 0.05 kg and a velocity of u1 = 900 m/s.
The person has a mass of m2 = 80 kg and a velocity of u2 = 0 m/s.
The final velocity is then: v = (m1*u1 + m2*u2) / (m1 + m2) = (0.05*900 + 80*0) / (80 + 0.05) = 0.56 m/s.
So after being hit by a browning bullet you'd be moving at 0.56 m/s which is about 1.25 mph. Assuming it hit your chest that would probably be sufficient to knock you off your feet unless you were braced, but you're not going to go flying. Of course an actual browning bullet would go straight through you so the actual knock back would be less.
The .500 S&W bullet gives a velocity of 0.17 m/s (0.4 mph) which would almost certainly not knock you over.
There's an assumption here that the bullet has to move the entire mass of the person of course, which is possibly not true - even hitting the chest, it would tend to move the torso but not the limbs, so actual speeds could be somewhat higher. If you assume half the mass is in the torso speeds would be double. Still nothing huge, it would be more a case of tipped off balance and maybe taking a step back than flying through the air.
Taking the browning bullet we have a mass of m1 = 0.05 kg and a velocity of u1 = 900 m/s.
The person has a mass of m2 = 80 kg and a velocity of u2 = 0 m/s.
The final velocity is then: v = (m1*u1 + m2*u2) / (m1 + m2) = (0.05*900 + 80*0) / (80 + 0.05) = 0.56 m/s.
So after being hit by a browning bullet you'd be moving at 0.56 m/s which is about 1.25 mph. Assuming it hit your chest that would probably be sufficient to knock you off your feet unless you were braced, but you're not going to go flying. Of course an actual browning bullet would go straight through you so the actual knock back would be less.
The .500 S&W bullet gives a velocity of 0.17 m/s (0.4 mph) which would almost certainly not knock you over.
There's an assumption here that the bullet has to move the entire mass of the person of course, which is possibly not true - even hitting the chest, it would tend to move the torso but not the limbs, so actual speeds could be somewhat higher. If you assume half the mass is in the torso speeds would be double. Still nothing huge, it would be more a case of tipped off balance and maybe taking a step back than flying through the air.
Use Psychology said:
I would not be surprised if a round stopped by a bullet proof vest would knock someone over.
It's simple physics!Newton correctly stated that for each and every action there is an equal and opposite reaction (or words to that effect). Which means that the person being hit receives the same amount of energy as the person who fired the weapon... So unless you are knocked off your feat firing a weapon you will not be knocked off your feet when you are hit. And last time I fired a weapon it did not knock me over in a dramatic fashion (I have not been hit by a round yet so cannot completely validate this hypothesis with my own research).
Now sure, we can be pedantic here. For example modern semi-automatic weapons will have a spring inside them which will spread the impulse of the energy over a slightly longer period of time, but again, this is a short period of time. So recoil might not be as "hard"...
But also the round will lose energy in flight and will rarely dissipate all its energy in the victim, most of the time it will go through them...
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