does a bullet fired into the air have the velocity to kill when it returns to earth?

Question

when a rifle or hangun is fired upwards the bullet inevitably returns to earth, will it kill if it hits a person, or will it lose velocity at it's zenith and fall harmlessly to earth ?

Answer 1

The bullet fired upwards will start at very high velocity (up to 1600m/s with high speed bullets), slow down dur to gravitation and air resistance, reach a certain level where it will stop, then start falling again toward the ground, receiving two forces in opposite direction: the gravity pulling it down, the air resistance slowing it "up".
It will accelerate until both forces (gravity and air resistance) are equal, when it will reach what is called its terminal velocity.
This velocity depends greatly of the shape of the bullet, and the fact that at that stage, it will be thumbling on itself.
Nevertheless, and without making calculations, it will fall at a very high speed, well over 300kph!
This is much slower that when it left the barrel,
But b**y high enough to make a serious hole in your skull...
Don't shoot happy bullets in the air...
(Just for info: a small bolt, M8x10, about the same as a bullet, falling from the 10th floor of a building WILL KILL YOU if it hits you on the head...)

Answer 2

It is not going to land at anything like the speed it went up. The velocity of a bullet leaving a gun is orders of magnitude greater than the terminal velocity it will achieve on the way down.

Whether or not it will kill you will depend on the drag coefficient of the bullet which determines the terminal velocity. I suspect the answer is no though unless it lands point down at 90 degrees to the top of your head.

A brick will hurt if dropped from 1m onto your hand because of it's mass, a bullet dropped from the same hight won't hurt at all because relativley speaking it has a low mass.

Answer 3

Yes it could (if it hits your toe, for example, it wouldn't kill).

As stated the bullet will have a terminal velocity depending on its air resistance against gravity, a standard bullet will tumbled to earth and, depending in its shape, most bullets will reach similar speeds if fired vertically regardless of whether fired from a rifle or handgun, larger bullets will have more air resistance but will have more energy due to greater mass.

A flechette or dart design of bullet will fall point first and will probably go right you. This type of munition is encased in a soft ballistic 'sabot' which disintegrates on leaving the muzzle. A single or group of darts them continue to the target, stabilised by fins to minimise the air resistance.

In WW1 larger versions of these flechettes where dropped from aircraft on troops occupying trenches and were able to penetrate steel helmets.

Answer 4

It is going to land at the same speed it went up, less the resistance of the atmosphere (which for a bullet will be as close to zero as you can get).
If you want to understand " 9.81m/s/s x Weight ".
Rest a brick on your hand, then drop a brick on your hand from 1m above it. Now you REALLY understand gravity.
And also why working out an objects drag co-efficient is sometimes irrelevant if it's your hand that's underneath the brick.

ps. a penny may or may not fall on it's side, depending on it's shape - so the 'Mythbusters' are good SFX guys just not good scientists.

Answer 5

Yes, it will have enough velocity to kill you.
The bullet will leave the rifle or handgun, to a maximum velocity of (say) 500m/s.
It will immediately be subject to an opposing force due to gravity (9.81m/s/s), and will de-accelerate to 0 m/s at its zenith.
It will reverse direction, accelerating at 9.81 m/s/s towards earth.
However, the shape of the bullet is still subjective towards air resistance, and will only reach a maximum speed of approximately 380km/p/h (240mph) on its return, which can still kill, depending on the overall mass of the bullet.

Answer 6

Yes it can kill. It is under the same acceleration the whole time (9.81m/s/s, which is the acceleration due to gravity). So if it starts at 50m/s (for example, thats not the actual speed), then it takes a certain distance to slow down. It then has that distance to get back to Earth. As it has the same acceleration, acting for the same distance, it will end up at -50m/s, i.e. 50m/s downwards.

Answer 7

So you didn't watch Mythbusters last night then? Cos that was their top question.

Wish I'd watched it properly now so i could answer you but i was lugging bunk beds round at the time!

I think one of the points they made was that they never fall straight back down and generally land sideways (at least 9mm do). most injuries caused this way are when guns are fired at an angle, not straight up.

The Discovery Channel website might have details?

Answer 8

It'd depend on the specific gun and bullet, but in many cases yes. It loses its velocity at the top end of its journey but provided it goes high enough would pick up sufficient velocity on the way down. You'd be seriously unlucky if you died this way.

Answer 9

It will be traveling at a speed high enough to kill but this will be much slower than the muzzle velocity it left the gun barrel at.

Imagine a small metal object hitting you on the top of the head traveling at very high speed......ouch

Answer 10

Yes