If you fired a gun upward, will the bullet have the same velocity as it goes down?

Question

I heard many people getting killed or injured from stray bullets from the sky, when irresponsible gun owners fire their gun in the air. This is prevalent in our country where there are wild celebrations during New Year's eve.

Answer 1

A fast bullet fires with a muzzle velocity of roughly 1,100 mph.

A falling bullet is slowed by air resistance from drag forces and lack of propellant means it falls at a MAX velocity (for a small bullet) of 150 mph, but normally closer to 120 mph.

Travelling at 10% of the speed, the bullet strikes with 1% of the total kinetic energy (compared to a bullet fired at someone). This means that a bullet fired straight up into the air is not likely to even seriously hurt when it strikes, much less to kill. You'd have to be VERY unlucky indeed to die from a bullet fired straight up.

The problem comes when you fire a gun upwards at an ANGLED ascent... the horizontal speed is NOT significantly slowed, so the bullet might strike as fast as... say... 50% of it's muzzle velocity... that's 25% of the kinetic energy (and enough to be more likely to injure or kill). People firing guns NOT straight into the air is the problem area.... even then, however, the chances of actually striking someone are still very low

Answer 2

No. A bullet firet upwards has an initial velocity imparted by the gun. It continues up until gravity stops it and it begins to fall. At that moment it begins to fall, it's velocity is zero, there is no initial velocity on the way down equal to the large initial velocity on the way up. The bullet will reach terminal velocity on the way down which is much slower than the intitial velocity it had moving up when fired from the gun. Than is not to say the bullet can't hurt you, it is still moving at least 120 mph.

If you shoot the bullet at and angle, say 45 deg. Then it retains 70% of its initial motion along the ground, so in this case it is much more dangerous. Most of the people injured by stray bullets are not from those fired straight up, but off at some angle. In this case the bullet retains a large portion of its initial speed when it hits the ground.

Answer 3

The bullet travels slower as it falls.

The bullet leaves the gun at a very high velocity, with a stable spin, and is still slowed by air resistance and gravity.

On the way down, it starts from a velocity of zero. Gravity will speed it up, but air resistance prevents it from travelling faster than its terminal velocity.

The bullet will still be travelling fast when it hits the ground, but one would have to be very unlucky to be killed by being hit by a falling bullet. The bullet is more likely to hit butt end first, which means that not only is the bullet travelling slower, the impact is spread out over a wider area. A falling bullet can still cause a pretty mean injury, just as being struck in the head by hail can cause injury, it's just not likely to be fatal.

Answer 4

No, it will not. The bullet is being forced out of the barrel of a gun at a very high velocity by gun powder. Once in the open it will begin to slow down do to drag, the force that is applied as it pushes against the air. At some point in time the air will slow it down to a point that gravity can no longer accelerate it. For humans falling out of an air plane it is ruffly 180mph. Buy if you could find the bullet after it came down you would see that it still does damage on the way down. It might not kill you but it will do some serious damage. Shot gun pellets will only rain like hail. Remember that hail falls from higher up and has ruffly the same aerodynamics as bullets and we don't get too hurt by that.

Answer 5

Myth Busters did this recently and the answer is no. On the way up due to the spin from the rifling in the barrel up it's a stable aerodynamic projectile, on the way down it tumbles and is less aerodynamic, receives more drag from the air, so it has a lower terminal velocity. Now if the experiment could be done in a vacuum the result would be the same speed, but in real world situations air resistance and aerodynamics causes the downward trip to be slower.

Another example of this would be a "tumble return" model rocket, such as the Estes Mosquito. It's descent is much, much slower then it's aerodynamic rocket powered ascent.

Answer 6

Discounting air resistance:

As the bullet travels upwards, it will gradually slow down until its speed reaches 0. Then it will begin to fall, gaining speed. The speed up is the same at the speed down, at the same point. For example, if the bullet left the gun at 1 meter off the ground, at speed x, when it falls back to the point of 1 meter off the ground, its speed will be x.

Accounting for air resistance:

The bullet will move slower due to the friction with the air, but it won't make enough of a difference to help the poor sap standing under it.

Answer 7

Almost...

More exactly, a bullet fired straight up will slow down due to gravity until it reaches a velocity of zero, then it will drop by force of gravity so that, *not* considering air resistance, it would reach the muzzle of the rifle at the same speed that it was discharged.

While the resistance from air will slow it somewhat, the bullet will nevertheess be traveling fast enough to do serious damage.

Answer 8

Yes, assuming that there is no air resistance, which will slow it's descent and ascent. Also consider wind resistance, which varies a lot, and create crosswinds to slow the bullet all the way down so it has the force of a small pebble dropped off the same height.

Answer 9

finally, a science question i know the answer to and its already been answered. the first guy is wrong, the others are right. the bullet cant go faster than gravity and wind resistance allow

Answer 10

mythbusters did an episode answering this question, when the bullet start to fall it will reach its terminal velocity, which is about 146 mph, and will not go any faster