[quote]does it presume a stable aerodynamic shape or can it account for roll and yaw disturbances?[/quote]
The Cd for a representative rifle bullet is about 0.15. As bullets go, a 0.3 Cd isn't considered that slick.
There are several ways of approaching figuring out what the Cd should be for a bullet like the .44, you can think of it as a short cylinder, you can take the Cd of an ogive, you can assume it's an imperfect sphere (think "golf ball"), you can average them all together. Most of the numbers group in the 0.3 ballpark.
The other thing to consider is that the effect of the Cd on the terminal velocity goes through that square-root when calculating drag, so a 20% error in the guesstimate would result in a 10% error in the terminal velocity, so it really isn't critical.
It also isn't all that repeatable, from one .44 to another, even if it's the same shape.
Weird thing, look up the Cd of a sphere, and you'll get a wide range of numbers. It isn't that the numbers are wrong or that no one has bothered measuring them, it's that slight differences in the conditions can result in big differences in the drag coefficient. With golf b@lls, for instance, those little dimples make about a 40% (IIRC) reduction in the Cd, compared to a perfect sphere the same size. If you take a perfect sphere and measure its Cd, then scribe a scratch in the surface and repeat the measurement, you'll get a significantly different result.
A lot of guesswork involved, so trying to nail down three-digit accuracy is pretty much a waste of time.
Since the length and diameter were within 0.01" of being the same, I just used the nominal caliber as the diameter. Compared to the uncertainty in the Cd, it shouldn't matter much.
Would you really feel safer if the force at-impact were 10% less than 2109 pounds?
If you shoot straight down with a gun at a person you will kill him.. But that is because the bullet will travel straight down beyond its terminal velocity..
The same cannot be said to be true if a bullet is shot straight up, reaches is apex and then starts travelling downwards. that bullet won't reach a speed faster than terminal speed.
If you also take in acount that the bullet probably will wobble and spin, then the probability for it having the speed and the kinetic energy enough to penetrate the skull will be quite low..
It will hurt, yes, probably a lot..But the chance for that kind of bullet killing a person is very slight.
I agree with charleskane. If a bullet was shot straight up (disregarding wind factor and even earth rotation) it would come down at no greater speed than terminal velocity.
Bullets are inherently unstable, that's why they are roation-stabilized. Also, usually they are made of lead with a copper coating or jacket which makes them heavier at the back than at the front. Therefore, when it eventually slows down/stops rotating it will fall down "butt first".
It's a bit like the "can you kill someone by throwing a coin off the empire state building" myth...
This message has been edited. Last edited by: mythmod,
Terminal velocity is plenty enough, if the poor fella was looking up, possibly with his mouth open at the same time. Now, can Adam and Jamie construct a rig to test that? As there was no mention of where the falling bullet may enter, i.e eyes or mouth.
quote:
Originally posted by qbfh1234: I agree with charleskane. If a bullet was shot straight up (disregarding wind factor and even earth rotation) it would come down at no greater speed than terminal velocity.
Bullets are inherently unstable, that's why they are roation-stabilized. Also, usually they are made of lead with a copper coating or jacket which makes them heavier at the back than at the front. Therefore, when it eventually slows down/stops rotating it will fall down "butt first".
It's a bit like the "can you kill someone by throwing a coin off the empire state building" myth...
Maybe Adam and Jamie believe that a falling bullet will not harm anyone, but the state of Arizona does not agree. In Arizona, they now have a law named after a 17 year old girl who was enjoying a pleasant evening in her back yard in Phoenix when a bullet ripped into her skull and brain, killing her. They were able to locate the shooter, but were not able to do too much, as the legislators believed as Adam and Jamie do. The legislature passed a law, making it a felony to fire a gun in the air.
Maybe Adam and Jamie believe that a falling bullet will not harm anyone, but the state of Arizona does not agree.
They tested if a bullet fired STRAIGHT up would kill you if falling at terminal velocity.
If a common small arms bullet was falling straight down at terminal velocity, it probably wouldn't hurt you seriously.( I would think that it might be a different story with something like a .50 Cal. BMG. bullet and it's weight.)
IIRC, they had doctor testimony that if a bullet were fired at any angle other than straight up, that it could, and would keep on it's ballistic path, and could seriously injure or kill someone.
Durring my tour in Iraq, there were several incidents when 7.62 rounds fell through the tin roof of our fema trailers. I saw one for my self at camp victory. Not sure if fired at angle or strait up.
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