What goes up, must come down. In the case of a rifle bullet, it will go so far up, that upon re-entry it will continue to accelerate until the rate of accereration is matched by wind resistance. Rifle slugs are pretty wind resistant, which means it will be descending pretty close to the same speed as its muzzle velocity. If it hits a person on impact, it's a sure thing it will kill, or at least severly wound, that person.

The bullet will exit the muzzle with a velocity, v (init). It will begin accelerating at -g, about 9.8 m/s^2. (Incidentally, we call this "falling" in normal english, even though it is moving upward, and any unpropelled projectile will do this, regardless of the angle of launch.) Most high-powered rifles fire at over the speed of sound (that "crack" when it is fired is the sonic boom!). It will move upward, and decelerate, and then it will peak in its trajectory. Then it will begin to move down, at a faster and faster speed. I have to say here that it will not come near the speed of its launch (muzzle velocity) since it needs external energy to break the sound barrier again. It will however be moving dangerously fast when it hits the ground, the experimenter or the rifle from which it was shot. In a vacuum, it would be very close to the muzzle velocity when it returned to its launch height, but not exactly, since the gasses expand even after the projectile leaves the barrel, and it is "pushed" a bit even outside the rifle! Terminal velocity for a small full metal jacketed slug? I don't know, but a human body can achieve >200 mph. I'd say a bit more, but no where near the speed of sound (~600 mph at sea level). The height could be estimated based on the time, especially if you could figure out how much air speed it takes to have the drag equal the weight (terminal velocity). Velocity would be constant after it accel'ed to that v. Hope this helps.

I am going to give you a lesson in Murphy's law. ;) While theoretically the behavior of the bullet is dictated by (only) it's muzzle velocity, the force of gravity, and the wind resistance of the bullet when it begins to fall again (which determines it's terminal velocity), there are all sorts of variables that APPLIED physics and the cruel forces of reality must take into account. These include, but are not limited to, temperature variations at different altitudes (affects air density, therefore terminal velocity is not constant), crosswinds (lateral displacement of the projectile), and a few other random factors. However, regardless of the specifics, it WILL come down somewhere with enough velocity to injure or kill someone.

On a body with no atmosphere, such as the moon, the rifle bullet would go straight up, reach a peak determined by the muzzle velocity and the strength of the gravitional field, and then begin to fall to the ground. When it passed by the muzzle, it would be moving at it's muzzle velocity, but in the opposite direction. On a body with an atmosphere, such as Earth, as the bullet travelled, air esistance would slow down the spin of the bullet around its axis, destabilizing it. Any kind of wind would also destablize the bullet and change its path. Also, as most rifle bullets tend to be tapered in one direction, when it reached its peak the combination of the slowing down of its rotation and the fact that the bottom of the bullet is flat would likely cause the bullet to begin to twist and turn randomly as it fell, dramatically decreasing the terminal velocity from a rifle bullet that is both facing the correct way and spinning. The bullet would impact the ground in the vicinity of its launch, but at much less than muzzle velocity. It could almost definitely still kill or injure. As an example, a fuel truck was destroyed in Baghdad shortly after Saddam Hussein was captured: celebrating Iraqis had fired their guns off into the air, and at least one of the bullets hit the truck and caused it to explode.

Well, essentially and in a nutshell, it will fall back down the same speed it went up. It may not be in the same spot due to angle, earth rotation, wind, unlucky birds, etc

Well, firing a rifle straight up when on Earth, will make the bullet fly sky high depending on the rifle and bullet type. As everyone knows, the bullet flys depending on the firing angle, before falling down in a dangerous speed, explaining it simply.

Long answer it comes back down really really fast, short answer dont do it!

That would explain the spate of HillBilly suicides recently!

It will fall.

it comes back down..where it lands..I know not where..LOL

Due to wind resistance, the rotation of the earth, and gravity, it will most likely arc, and come down in a position that you will have no clue of unless you can calculate wind speed and the parabola that is the bullet's trajectory. I wouldn't recommend trying this one. =)

Yikes! That hoits !!!

As a Police Officer I can say, the bullet speed will increase until it reaches its terminal velocity. The bullet reaches terminal velocity when the air drag equals the pull of gravity or stating it another way, the bullet weight and drag are balanced. Once this velocity is achieved the bullet will fall no faster. Wind can have a dramatic effect on where a vertically fired bullet lands. A 5 mile per hour wind will displace the 150 gr. bullet about 365 ft based on the time it takes the bullet to make the round trip to earth. In addition the wind at ground level may be blowing in an entirely different direction than it is at 9,000 feet. It is no wonder that it is so difficult to determine where a falling bullet will land.

It falls at the speed of about 150 mph and it can cause significant injury, but is most likely not fatal.

It can actually kill someone when it lands.

With my luck, I'd be in a helicopter flying over it at that exact moment. The bullet would pierce the fuselage and enter right into my left buttock. Luckily I'm already in a helicopter and they can take me to the nearest hospitals helipad.

In the West there's an insane tradition of shooting guns in the air at midnight on New Years. A couple of years ago in Albuquerque, one came down into a two year old's head.

************ I think that I need a clarification here. A couple of people have already failed to read the entire answer and down rated me because the obviously misunderstood what I was stating. I am not saying that firing a gun in the air is not potentially deadly. I am addressing narrow case of shooting straight up. The Mythbusters actually tested this. Their methodology was sound and showed that a bullet fired STRAIGHT up will not come back down at a velocity that is even sufficient to break skin. So, please read THE ENTIRE ANSWER befor you rate it or leave a comment stating that I don't know what I am writing about. ************ No one here has gotten the right answer. A bullet fired straight up will not come back down with enough force to do any serious injury. This is because as it goes up its spin will slow and it will begin to tumble on the way back down. This tumble will prevent the bullet from achieving a dangerous velocity on the way back down. However, very few people are able to fire a bullet straight up. If you don't get the bullet going straight up, then it follows a parabolic trajectory. If this happens then the the bullet can maintain its stability and a significant portion of its muzzle velocity. Thus it can come back down with enough speed to actually do serious damage. This is what actually happens in cases where people or things are injured by bullets shot into the air. So, it is still a bad idea. I got this information from the Mythbusters. They actually tested this by dropping bullets in a vertical wind tunnel and placing guns in mounts that would hold them vertical. All of their test shows that a bullet fired straight up will not return to earth with sufficient velocity to cause serious harm. If you stop and think about it for a minute this should actually make sense. How many people are killed by pea sized hail? Hale would probably have a higher terminal velocity than a bullet because it doesn't matter if it tumbles. The nearly spherical shape of the hail will have the same air resistance no matter what face is leading. It takes pretty large hailstones to really do damage. So, simply falling out of the sky, a bullet will not pick up enough speed to be dangerous. It has to be on a parabolic course (which will be the case the vast majority of the time a person fires a gun into the air) in order to be dangerous.

What goes up, must come down ... the bullet will fall back. There have been a significant number of people shot and killed in the middle east by people who just fired their guns upward while cheering.

The bullet will come down at the speed of about 150 mph, and cause serious injury, but death is unlikely. Check this out for more info... http://blogs.chron.com/sciguy/archives/2006/12/how_hazardous_a.html

The bullet would come straight back down hopefully avoiding anything in its path.

If you fire directly upwards it will come back down at the same spot. If your lucky there will be a breeze, which could save your life. Celebratory gunfire (mideast) is idiocy. ALWAYS control your rounds.

4 things can happen... 1 nothing 2 hits the ground safely somewhere 3 hits you, your friends, your kids, someone else and kills you or them 4 you go to prison ive seen the mythbusters...but this is not conclusive... firing a few dozen or even hundreds of rounds into the air...rifle , pistol, even b b guns... if the bullet maintains its attitude...straight and doesnt tumble..it can still kill you... straight up, angled, etc...dont do it ..it is dangerous... to children, animals, plants, adults and machinery etc

One of Sir Issac Newton's most important laws of Physics, the FIRST LAW OF MOTION states that "What goes up, must come down". Bullets are no exception to the laws of physics.

I do not believe myhtbusters. I'm sorry but I take everything they say with a grain of salt. I haven't seen it done. But to test it, I would personally take a bullet up to the height it should reach when fired, and then drop it base first and see what happens.

It will come back down and bop you on the head. :)