# How Big of a Bullet

AThousandYoung
Posers and Puzzles 07 Mar '08 23:50
1. AThousandYoung
07 Mar '08 23:501 edit
How big of a bullet does it take to knock a man over? Assume he's wearing full body armor; the full energy of the bullet is absorbed. Let's suppose it hits him in the chest.

I'm not talking about a man falling over because he's wounded. I mean he falls over due to the force of the bullet hitting him and bowling him over.
2. 07 Mar '08 23:521 edit
Originally posted by AThousandYoung
How big of a bullet does it take to knock a man over? Assume he's wearing full body armor; the full energy of the bullet is absorbed. Let's suppose it hits him in the chest.

I'm not talking about a man falling over because he's wounded. I mean he falls over due to the force of the bullet hitting him and bowling him over.
how tall is the man, what's he stood on, in what pose, and does the bullet damage him?

edit: exclude the damage question - you've already said he's not wounded!
3. AThousandYoung
07 Mar '08 23:552 edits
Originally posted by pineapple42
how tall is the man, what's he stood on, in what pose, and does the bullet damage him?

edit: exclude the damage question - you've already said he's not wounded!
Six feet, standing straight, feet together, hands at sides, shoulders squared, he's on a solid planar surface (concrete, say). He is hit in the sternum.

I already know a normal rifle round won't do it.

4. sonhouse
Fast and Curious
08 Mar '08 00:38
Originally posted by AThousandYoung
How big of a bullet does it take to knock a man over? Assume he's wearing full body armor; the full energy of the bullet is absorbed. Let's suppose it hits him in the chest.

I'm not talking about a man falling over because he's wounded. I mean he falls over due to the force of the bullet hitting him and bowling him over.
How big the bullet is has nothing to do with it. What you mean is this: How much kinetic energy does it take in a bullet against someone wearing a bulletproof shield for that person to be knocked over' So a 22 going 1000 meters per second would have roughly the same kinetic energy of a 45 going 400 meters per second, having the same kinetic energy, they would impart the same thrust to the person, so its a matter of how much kinetic energy it takes to bowl a person over. What that energy would be depends on the person. A 6 foot wimp coming in at 100 pounds would certainly be easier to knock over than refrigerator Jones for instance.
5. 08 Mar '08 09:39
Isn't momentum the thing to look at here, and not kinetic energy? Momentum will be conserved in the collision, but kinetic energy will not (unless the bullet rebounds elastically, which is unlikely).
6. wolfgang59
Mr. Wolf
08 Mar '08 11:17
Yes momentum is conserved, kinetic energy is not.

Another way to look at it is what force (F) is imparted to the man? Thats from

Ft = mv *

where mv is the momentum (before impact) of the bullet and t is the time the bullet takes to decelerate to a stop. This time element t will obviously depend on the construction of the bullet proof jacket.

* Assuming the bullet's momentum is negligible as the man falls!!
7. AThousandYoung
08 Mar '08 18:364 edits
Originally posted by sonhouse
How big the bullet is has nothing to do with it. What you mean is this: How much kinetic energy does it take in a bullet against someone wearing a bulletproof shield for that person to be knocked over' So a 22 going 1000 meters per second would have roughly the same kinetic energy of a 45 going 400 meters per second, having the same kinetic energy, they wou ...[text shortened]... in at 100 pounds would certainly be easier to knock over than refrigerator Jones for instance.
Standard rifle cartridge ratio between powder and bullet. 200 lbs. Average proportions.

Would a 0.50 BMG do it? How about a Napoleonic cannonball shot (assuming the above powder to slug ratio)?

We also need to determine how hard the guy needs to be hit to be knocked over. That's not an easy bit of information to find.
8. smw6869
Granny
09 Mar '08 01:41
Originally posted by AThousandYoung
How big of a bullet does it take to knock a man over? Assume he's wearing full body armor; the full energy of the bullet is absorbed. Let's suppose it hits him in the chest.

I'm not talking about a man falling over because he's wounded. I mean he falls over due to the force of the bullet hitting him and bowling him over.
I've read that there is not a bullet made that has enough power to knock a man off his feet, even without a bullet proof vest on. Which nerves or nerve system a bullet strikes determines which way a person will fall. Some people get an in and out wound but they keep coming at you....until they bleed out.Rockets and artilery rounds are not considered bullets. That's all i know.

G.
9. AThousandYoung
09 Mar '08 06:08
Originally posted by smw6869
I've read that there is not a bullet made that has enough power to knock a man off his feet, even without a bullet proof vest on. Which nerves or nerve system a bullet strikes determines which way a person will fall. Some people get an in and out wound but they keep coming at you....until they bleed out.Rockets and artilery rounds are not considered bullets. That's all i know.

G.
The bullet proof vest would actually HELP the bullet knock the man off his feet. Without it a powerful round would go straight through and keep some momentum in the process.
10. smw6869
Granny
09 Mar '08 17:18
Originally posted by AThousandYoung
The bullet proof vest would actually HELP the bullet knock the man off his feet. Without it a powerful round would go straight through and keep some momentum in the process.
I saw a video once where a guy held a large telephone book on his stomach. Another guy shot a 50 cal. round at it and the round had no affect on knocking the other guy over. DON"T TRY THIS AT HOME. like i did.

G
11. AThousandYoung
09 Mar '08 18:29
Originally posted by smw6869
I saw a video once where a guy held a large telephone book on his stomach. Another guy shot a 50 cal. round at it and the round had no affect on knocking the other guy over. DON"T TRY THIS AT HOME. like i did.

G
Telephone book?

Those things go through engine blocks...
12. smw6869
Granny
09 Mar '08 22:30
Originally posted by AThousandYoung
Telephone book?

Those things go through engine blocks...
They use armor piercing bullets to go thru metal. I'm sure in the film they were using lead bullets. I'll look for the video.

G.
13. AThousandYoung
10 Mar '08 05:331 edit
Originally posted by smw6869
They use armor piercing bullets to go thru metal. I'm sure in the film they were using lead bullets. I'll look for the video.

G.
Ah, that makes sense.

It might also have been a .50 cal PISTOL round, and not a BMG.
14. TheMaster37
Kupikupopo!
10 Mar '08 11:53
Cannonballs knock people over.
15. AThousandYoung