What would the results be of firing a firearm on the surface of the moon?

Question

A bullet contains its own oxygen

Answer 1

Crater Penny is one (quite small) possibility!

When the bullet landed, it would create a mini crater. That's how we think that the craters on the Moon were made, except that the "bullets" in that case were bits of stuff left over from the formation of the solar system, finally plowing into the Moon. Of course, their speeds were very much faster than those produced by the typical firearm. (They were typically moving at the Moon's "escape velocity" or greater, which is worked out in a postscript below.)

Interestingly, it was once thought that the craters might be a result of volcanic activity. The idea that a projectile could come in at any old angle, even a very shallow one, and then create a round crater, seemed very far fetched. However, someone on Earth took a rifle, and fired it at various angles into sand or mud. Lo and behold: basically round craters!

Live long and prosper.

POSTSCRIPT: I don't think we need worry about the bullet escaping the Moon's gravity, or even going into orbit around it.

The "escape velocity" (really: "speed") from the surface of an essentially spherical astronomical object is given by:

V_esc^2 = 2 G M / R,

where G is the Constant of Gravity, M is the mass, and R is the radius.

Plugging in the values of G, M_moon, and R_moon in your favourite system of units, you should find that:

V_esc (moon) = ~ 8,550 km/hr or ~ 5,310 mph.

(Two of my inputs were only given to 3 sig. figs. in the reference at hand.)

It's always good to have a way of checking such a calculation, and here's one:

My vague recollection is that Earth's escape velocity is between 24,500 and 25,000 mph. O.K. then; using 'm' for moon, and 'e' for earth, we should have that:

V_esc (m)/V_esc (e) = sqrt [(M_m/M_e) x (R_e/R_m)].

This is beautifully organized for a quick calculation, because

M_m/M_e = ~ 1/81, and R_e/R_m = ~ 4, and guess what?:

BOTH of these numbers involve perfect squares! Let's work V_esc (moon) out crudely then, using 25,000 mph for Earth.

With these inputs, V_esc (moon) will be ~ 25,000 x 2/9 mph, or ~ 5,560 mph.

(24,500 mph for the Earth would give ~ 5,440 mph for the Moon.)

So it checks out as well as could be expected, given the crudity of the inputs for these later calculations.

No simple firearm could send a bullet or shell at speeds remotely approaching these, so there's no danger of having them escape completely.

Nor will it orbit and later hit you in the back of the head. The circular orbit velocity is related to the escape velocity by:

V_(circ. orb.) = V_esc / sqrt 2.

So V_(circ. orb.)(moon) = ~ 5,310/1.414...mph = ~ 3,760 mph, again far greater than a bullet or shell shot from any simple firearm.

Answer 2

You might hit a space duck! But seriously, if you pointed the gun straight up, the bullet would escape the gravitational field of the moon and be on its merry way across the universe. The moon does have gravity, but it has only 1/6th the gravity of the earth and it has a very minimal atmosphere to slow the bullet down on its way out. Note: if the bullet requires oxygen to ignite, there would obviously be a problem, but i don't think it is required.

follow up: after further review, I concur with the rather lengthy proof above. Not enough juice to escape the moon's gravity. I'd still watch for space ducks tho ;)

peace

Answer 3

Assuming of course that you bring some oxygen to allow the combustion of the gun powder....

Depends on where you point it and how powerful the gun is.

If you point it down, it simply blasts into the surface.

If you point sideways, it flys along (no air resistance) the gravity curve and either
a) isn't fast enough and eventually comes down into the dirt.
b) is just fast enough that it goes sideways as fast as it oges down and thus never hits the ground, or is in orbit.
c) goes way too fast and escapes altogether, flying off into space never to return.

It just depends.

(if this is fo school you might want to talk about the orbit thing...)

Answer 4

The bullet would fly out of the gun and you'd probably get pushed back to the point where you might get knocked over since you'd weigh less. Of course for the same launch angle, the bullet would go much further.

Answer 5

Well, there'd be a bullet hole. It may be slowed down, since you are in a vacuum, but about the same thing as if you shot it on Earth.

Answer 6

I'm going to have to say that the gun would not fire - as the gunpowder in the shell can not burn in an absence of oxygen.

Answer 7

the bullet from your firearm would not do any hole on moon's surface