Stray Bullets: Duck and Cover?

[ElusiveMiser]

I’ve heard that there are stray bullets flying around in the atmosphere, just waiting to hit something. I assume this is somewhat true, but to what degree? It seems like your average bullet fired from your average gun wouldn’t have enough velocity to escape the earth’s atmosphere, and would eventually fall back to the earth. But would it fall? Or would it just cruise around in the lower atmosphere at a dangerous speed? I’m sure that depends on what angle it was fired from, but just in general, where do those bullets go?

[Bear_Nenno]

Where did you hear this? I would think bird poo is a bigger danger.

[Duck_Duck_Goose]

Duck here. Still waiting for Cover to show.

I assume this is somewhat true…

Nah, it’s not true at all.

The escape velocity for Earth is
http://www-star.stanford.edu/projects/mod/ad-escvel.html

…11.2 kilometers per second. This is the velocity that an object (or gas molecule!) needs at the surface of the Earth to be able to overcome the gravitational attraction of the Earth and escape to space.

How fast does a speeding bullet travel?
http://hypertextbook.com/facts/MariaPereyra.shtml

The 0.22 rimfire cartridge, which has a very small powder charge, sends its bullets on their way at between 370 m/s and 460 m/s. Cartridges in rifles – centerfire cartridges – propel their bullets at a much faster rate. The 0.220 Swift, which drives a very small bullet at over 1220 m/s, is the cartridge with the highest velocity.

A speeding bullet is not traveling 11 kilometers per second. It is traveling, possibly, 1220 meters per second.

A bullet, like a meteorite, wouldn’t just cruise around in the lower atmosphere. It would fall to Earth sooner or later. That’s what gravity does, is pull things back down to Earth.

[Zebra]

No the bullets return to earth and occasionally hit and kill people. I know in Phoenix AZ people are working on makeing it against the law to just randomly fire your guns in the air. (people do this at New Years and at other times like they are in some sort of old west movie) When the bullets come down they have to hit something. Since the population of the Now West is much greater than the Old West the bullets sometimes hit people.

Now up in space there are bits of space debris. Pieces of rocets and such that are orbiting around at great speed. Maybe that’s what you are thinking of?

[Duck_Duck_Goose]

Uh-oh. Math.

I think that this chart http://www.cartest2000.com/images/jbmaximumrange.jpg

shows how high up a bullet will travel if you point the gun straight up (at 90 degrees). If I’m reading it right, it says that the bullet will travel 25 times 10 to the second power yards, and 10 to the second power is 10 times 10 which is 100, so 25 times 100 is 2500. Times 3 for yards, so 7500 feet. Yes? A gun pointed straight up will fire a bullet 7500 feet up into the atmosphere, or just about to Piper Cub cruising range.

Is that what you’re talking about, the UL about stray bullets hitting a small plane? I suppose it could happen, but it wouldn’t be a bullet that had been cruising around in the atmosphere for a while, it would be a bullet that someone had just fired, down on the ground.

Here’s the whole ballistics website.
http://www.cartest2000.com/jbtouran.html

The Maximum Range plot shows the maximum distance the bullet will travel if fired from an angle ranging from 0 to 90 degrees. Also shown on the plot is the altitude the bullet will reach if fired at that angle. With atmospheric drag, the angle of maximum range usually occurs at just over 30 degrees. In a vacuum, the maximum is at 45 degrees.

[Lord_Jim]

Here’s what Unca Cecil has to say about bullets shot up in the air. Can a bullet fired into the air kill someone when it comes down? He’s not very conclusive about the likelihood of being killed by a bullet, but he did site reports of death by stray bullets.

He also used a phrase that may answer part of your question, “what goes up must come down”. And in the test he sited, they come down at about 300 feet/second and hit about as hard as a whack with a hammer.

Jim