physics of a falling bullet


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faustulus
January 1, 2003, 08:19 PM
Every year there is speculation about people shooting into the air and the bullets falling to earth and killing someone. I really have a problem with this. The physics don't seem to match, I realize a baby or something but it is the equivilent to dropping a quarter off the empire state building. There comes a point where the bullet reaches terminal velocity and I don't think it contains enough energy to kill. Say a 200 grain bullet at 9.8m/s2.

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Redlg155
January 1, 2003, 08:32 PM
A bullet fired straight up? No.

A bullet fired at a 45 degree angle? I would think Yes.

An arrow with a broadhead? Definitely Yes.

Good Shooting
Red

Shawn Dodson
January 1, 2003, 08:39 PM
In the Bay Area during the early '90s, a woman was hit in the leg by a .30 caliber bullet, fired either during New Year's or 4th of July, I can't remember which.

Anyhow, a few miles away, in a different jurisdiction, someone calls police on a guy who's shooting his 30-30 into the air. Police catch the guy, and after they hear about the woman's injury, they match the bullet to the guy's rifle.

I reckon most people don't shoot their guns exactly straight up into the air.

I remember standing out on my front porch in Sunnyvale, CA on New Year's 1992, hearing handgun bullets whizzing/buzzing past me as they traveled down my street, fired into the air by someone up the block. I immediately went back inside.

Drjones
January 1, 2003, 09:42 PM
Actually, there have been several people killed in Greece by falling bullets.

Us crazy Greeks have a penchant for shooting guns into the air, you see...:rolleyes:

I am quite sure that a quarter dropped off the Empire State bldg. would have far more than just "enough" speed to kill and more...

New_comer
January 1, 2003, 09:56 PM
We now have two dead caused by a bullet which fell on their heads at last night's celebrations. :(

Free-falling parachutists reach about 125 MPH of terminal speed. It's not hard to believe that a slug could attain much a faster speed due to its smaller cross section and heavier density.

I've seen a news report sometime ago about a 45 slug piercing a galvanized iron roofing, the quarter inch plywood ceiling, finally embedding itself in a half-inch cabinet plyboard.

It definitely has enough oomph to pierce an adult human's skull... :(

Drjones
January 1, 2003, 10:00 PM
Agreed newcomer. Thank you!

Man, honestly, WHAT are your chances of getting hit by a falling bullet? You must have the WORST luck imaginable!!! :(

I heard that even a penny dropped from the top of the Empire state or like building has huge destructive potential. Anyone know for certain?

RKCheung
January 1, 2003, 10:07 PM
Funny that this topic came up, I just looked this up yesterday.

Coins that are thrown off the Empire State Building supposedly get picked up by the updraft around the building and get pushed to a nearby ledge.

Let me look for the link...

Here it is: Empire State Building (http://exchange.liveperson.net/LP/Int3FaqDetails.cfm?C=%24%29%285%21R%20%20%20%0A&Faq=1&Action=%261%2D88C3Q%5E%0A&FaqID=%25%29H%2D%2CS%26Q%5E%0A&SearchTermFaq=%24%3D%2DP0D6Q%5E%0A&SearchTermOrig=%24%3D%2DP0D6Q%5E%0A&CategoryID=%24%3E%3DP7FFQ%5E%0A&SearchType=%235MT%20%0A&FaqsDisplay=10&NewSearch=0&Popup=No&cfid=1998675&cftoken=61969608)

Due to the shape of the building, when wind blows against it, it is driven up, creating "updrafts" -- if coins are tossed from the top, the wind blows them against the building and they drop on one of the setback roofs -- usually coins from 86 drop to 80 and when the electricians are changing the color gels they collect the loose change. Coins and other objects do not make it to the street; roofs of cars and buses are not crushed, people are not killed and holes are not made in the streets and sidewalks. Perhaps when it is very windy these objects are carried off to New Jersey or into the river.

Bruz
January 1, 2003, 10:18 PM
Every year there is speculation about people shooting into the air and the bullets falling to earth and killing someone.

It's true, saw it on a movie, "The Mexican", with Brad Pitt. :scrutiny:

waterdog
January 1, 2003, 10:24 PM
We have a new law (Shannons Law)against firing guns into the air here in AZ, it's a felony.

This teenage girl was in her backyard in the middle of Phx, when she was struck in the head by a falling bullet.

If you have an ND, and the projo travels in an upward direction, you have commited a felony.

Pretty stupid law, if you ask me.

waterdog

Drjones
January 1, 2003, 10:38 PM
RK: Thanks! I didn't know that! Cool!

Let's assume there is no wind, and the coin IS able to fall straight down...what then?

45R
January 1, 2003, 11:01 PM
We have a new law (Shannons Law)against firing guns into the air here in AZ, it's a felony.

This teenage girl was in her backyard in the middle of Phx, when she was struck in the head by a falling bullet.

If you have an ND, and the projo travels in an upward direction, you have commited a felony.

Pretty stupid law, if you ask me.

waterdog

There are several rules of gun safety. This was obtained on Glocks website though there are variations of the rules the basics remain the same.


1) Handle all firearms as if they were loaded!

2) Always keep your firearm pointed in a safe direction!

3) Keep your finger out of the gun's trigger guard and off the trigger until you have aligned the guns sights on a safe target and you have made the decision to fire!

4) Always be certain that your target and the surrounding area are safe before firing!

Remember that a bullet can travel as much as several miles, so you should be certain of what your bullet could strike before you pull the trigger. Never fire at a movement, a noise, a flash of color or a rustling bush without positively identifying your intended target.

Firing a gun in the air would be a breach of rule 4. Shooting your gun into the air is not considered proper gun safety. PEOPLE HAVE BEEN KILLED FROM STRAY BULLETS FIRED INTO THE AIR. Felony, Stupid Law or not, the fact of the matter is that we have to have rules and regulations to prevent incompentant acts such as the ones mentioned above. Gun owners are responsible for every bullet that leaves the barrel.

Respectfully

45R

nemesis
January 1, 2003, 11:18 PM
Free-falling parachutists reach about 125 MPH of terminal speed.

Actually, it depends on body position. You can actually hit over 200 mph in a head down dive. Make sure you flare well ahead of deployment or it can hurt.

A couple of years back, on New Years Eve; a bullet came down through the roof of a mobile home, hit a young girl in the head and killed her.

That isn't a theory.

Deadhand
January 2, 2003, 12:39 AM
During the mid Eighties, in Bakersfield, California, a guy in the South end of town returned from a deer hunting trip. While unloading his truck, he somehow discharged his .270 into the air. He was horrified to learn the following day that a groundskeeper at a cemetary in the North end of town had been shot and killed by "a stray shot". The gardener was sitting on a curb eating his lunch when the round hit him in the head. The shooter was prosecuted for the negligent homicide, but received a light judgement. The following lawsuit was not so lenient, however.

cratz2
January 2, 2003, 01:11 AM
Yeah... keep in mind that 9.8m/s/s is the acceleration not the terminal velocity. Have you ever been hit by a decent-sized piece of hail? I have - and it hurts. Imagine that but instead of being tearshaped and hitting with the round or un-pointy end, hitting you with a sharp end of a spitzer bullet.

Have a friend thats a bit of an anti ever since one fourth of July, he went out to discover that a rifle bullet had fallen down into his car, through the roof and into the passenger seat.

Mike Irwin
January 2, 2003, 01:17 AM
Fast,

Everything depends on the angle at which the bullet is fired.

Robby from Long Island
January 2, 2003, 02:00 AM
I worked in Manhattan and the surrounding boroughs for 35 years and never heard about, read about or saw on TV a story relating to anyone being injured or killed from coins or small objects being thrown or dropped from tall buildings.

While it's true that the Empire State Building has ledges on some of its levels and anything dropped over the side from the top observation level will be blown back to some levels below, if a person were so inclined to with all their strength hurl a quarter over the side it would definitely go all the way to the ground.

I was working on the 16th floor of the north tower of the WTC when it was hit and saw many solid objects both small and large sailing by the windows and don't feel if anything as small as a coin or bullet falling straight down had enough velocity to kill anyone underneath. I think any solid object from the 80th or above floor by the time it reached the 16th had already achieved maximum velocity.

I remember reading long ago that solid objects regardless of size drop at the same velocity. In other words, if you dropped a bowling bowl and a golf ball from a 5,000 foot height, both would hit the ground at the same time. After freefalling a certain distance, solid objects reach maximum speed and no longer increase their rate of velocity but maintain that same speed until impact with the ground.

The above is just my personal opinion and at this time have no facts to back it up. But at the same time I wouldn't want to be the guy trying to catch that .30 round that was fired straight up.:D

Safe shooting.

Mike Irwin
January 2, 2003, 02:08 AM
"if you dropped a bowling bowl and a golf ball from a 5,000 foot height, both would hit the ground at the same time."

There was an interesting article in National Geographic on gravity and space some years ago that stated that research was indicating that it was actually possible for some dense objects to fall to early more slowly than less dense objects.

IIRC, apparently the denser an object is, the more it will repel against gravity, sort of like trying to click similar poles of two magnets together.

I've got that around here somewhere. I'll have to dig it up.

How does it related to this discussion?

Beats the heck out of me. :)

Robby from Long Island
January 2, 2003, 02:39 AM
Mike,

It would be interesting if you could find that article you mentioned. It would be interesting if we could find out what the actual rate of velocity would be for a large caliber bullet falling freefall to earth.

I can visualize a marshmellow not falling at the same velocity as a golf ball straight down due to density differences but a bowling ball vs a golf ball.........

But that density factor would be of great interest to more than just me I'm sure. Anyway, time for a nap.


Safe shooting.

45R
January 2, 2003, 02:50 AM
Information on this subject is located in the Jounal of International Wound Ballistics Assoc. 1995 Vol2, No1 page 21. Article written by L. Hagg

I have the article. If anyone is interested I can send it to them. Its scanned in PDF format and over 2megs.

PM me with email address

EDIT: information on falling bullets can be found, not to be confused with the NG article

faustulus
January 2, 2003, 03:06 AM
Imagine that but instead of being tearshaped and hitting with the round or un-pointy end, hitting you with a sharp end of a spitzer bullet.

exactly my point, if hail doesn't kill you it would seem a bullet wouldn't.

Everything depends on the angle at which the bullet is fired.

Past a certain point it shouldn't, vertical velocity and horizonal velocity are not connected, so in theory at a 45 degree angle, yes but anything approaching 90 should have no effect. A bullet fired from a gun and dropped beside the gun will hit the ground at the same time.

I can visualize a marshmellow not falling at the same velocity as a golf ball straight down due to density differences but a bowling ball vs a golf ball.........

The only thing that would effect the two would be lift of the bodies. One golf ball weighing 3 grams would fall at the same rate as a golfball weighing 3lbs of course the 3lb ball would have to be more dense, but that should not effect the rate of desent.

Information on this subject is located in the Jounal of International Wound Ballistics Assoc. 1995 Vol2, No1 page 21. Article written by L. Hagg

I would love a copy if it wouldn't be too much trouble.

Mind I am not saying that it doesn't happen, I am just interested in the physics of the event. The odds would seem to be stacked against it happening as much as the stories make it out.

45R
January 2, 2003, 03:16 AM
I managed to get the Pdf article on my geocities account

It can be obtained here.

http://us.share.geocities.com/pbear222/falling.pdf

Copy and paste to another window or it wont work for some reason.
Nothing like science and peer reviewed evidence. :) I'll get a chance to read it tomorrow morning!

Apple a Day
January 2, 2003, 06:36 AM
A bowling ball and a golf ball dropped from the same height would hit at the same time NEGLECTING AIR RESISTANCE That is why a person spread-eagle reaches terminal velocity at ~120mph while ~200mph in a pike position. -9.8m/s^2 (-32.2ft/s^2) is only good for short distances or in a vaccuum.

Terminal velocity is the point at which the resistance due to air reaches the point to where it is equal to the weight of the object pulling it down. If you shoot a bullet into the air (nice streamlined object) it will still come down with considerable velocity. I remember seeing that a .3030 bullet would come down at ~300feet/second. Hit the right spot and it's lights out.

By the way, shooting at an angle isn't going to do much one way or the other. I am sure the bullet would reach terminal velocity anyway unless the angle was shallow.

If you shot a bullet straight up into the air then it wouldn't hit you on the head anyway. There is something called the Careolis effect(sp) which is a way for accounting for the rotation of the Earth. Literally, you would rotate out from under the bullet before it came back down. It would be close, though.

gruven
January 2, 2003, 08:04 AM
http://www.loadammo.com/Topics/March01.htm

"Based on the results of these tests it was concluded that the bullet return velocity was about 300 f.p.s. For the 150 gr. bullet this corresponds to an energy of 30 foot pounds. Earlier the Army had determined that, on the average, it required 60 foot pounds of energy to produce a disabling wound. Based on this information, a falling 150 gr. service bullet would not be lethal, although it could produce a serious wound."

JohnBT
January 2, 2003, 11:52 AM
From How Do Bullets Fly at www.nennstiel-ruprecht.de/

Lots of good reading there. It never occured to me that a bullet shot straight up would fall base first.

"Q: If a bullet is fired vertically from a rifle, what will its terminal velocity be if it strikes the top of someones head on its way back down?

A: This question is hard to answer in general. The best I can give is a "worst-case" estimation.
When a gun is fired vertically, the bullet after some time reaches a summit where the velocity is zero, and then falls back. The bullet will fall back base first which is hard to calculate. I can estimate the velocity if it would fall nose first, that is the normal flying position for which drag is well known - so the real terminal velocity will actually be smaller than the following prediction.

For a .22 lr bullet (m=40 grain, v0 = 1150 ft/s)
the summit will be at 1164 ft, the total flight time 30 seconds and the terminal velocity 270 ft/s
For a SS109 military bullet (m= 55 grain, v0=3200 ft/s)
the summit will be at 2650 ft, the total flight time 44 seconds and the terminal velocity 404 ft/s.
For this bullet are indications that it will become unstable. This will further reduce summit height and terminal velocity considerably. "

Justin
January 2, 2003, 12:07 PM
Every time a bell rings, an angel gets its wings.

Every time a bullet negligently shot into the air lands near a person, HCI gains a member.

:uhoh:

para.2
January 2, 2003, 01:45 PM
Last New Year's Day (2002) I came out in the morning to find a brand-new hole in my windshield, and an ( apparently)7.62 AK bullet on my dash board. Bullet didn't have enough velocity to penetrate the dash after going through the glass, but if that had been somebodies head?....:uhoh:

Drue
January 2, 2003, 01:59 PM
On New Years Day, 1992 I found a hole in my windshield and a 230 FMJ .45 slug on the floorboard of my car. The bullet may have deflected somewhat passing through the windshield but a stringline between the hole and the dent on the floorboard indicated that it was going almost straight down.
I still have the slug.

Drue

Mike Irwin
January 2, 2003, 02:22 PM
Fast,

My comment addressed this statement in your first post...

"Every year there is speculation about people shooting into the air..."

The word UP leaves a lot of room for interpretation.

Technically, 1 degree above horizontal is up.

I sincerely doubt that anyone who is stupid enough to fire randomly into the air is really concerned about getting the muzzle of the gun elevated to the point where the returning bullet isn't going to do any damage.

Hence my comment regarding angle.

Frohickey
January 2, 2003, 02:53 PM
As far as objects of different densities falling at different rates, its not density related, but air resistance related.

A theoretical 'point mass' of infinite density will fall at the same rate as a theoretical 'line mass' of zero density.

A 'heavier' object would fall at a faster rate than a lighter object, but this would be imperceptible. Gravitational attraction is related to the masses of both objects. Earth is very massive. Falling object is not.

As far as terminal velocity of a bullet fired into the air, it all depends on air density, the type of bullet, the angle its fired at, and the muzzle velocity. Its really about how much elevation the bullet was given, the amount of air resistance the bullet encounters, and 32 ft/sec^2 that gravity gave it. But that only counts the vertical velocity. There is also the horizontal component too.

The cops I knew that worked on New Years Eve usually find an excuse to either be indoors during the 15 minutes before and after the stroke of midnight, or they just happen to be under a freeway overpass. :D

Mike Irwin
January 2, 2003, 04:03 PM
"A 'heavier' object would fall at a faster rate than a lighter object, but this would be imperceptible. Gravitational
attraction is related to the masses of both objects."

Fro,

I'm still looking for the article, but check my note above about denser objects seeming to have some sort of repulsion effect.

Blew my mind when I first read it.

GinSlinger
January 2, 2003, 04:34 PM
Mike--I too have seen that article ("In Search of the fith force" or some-such). Article also related that certain articles tested had different "repulsive" forces. That article was about how, even as physics was coming closer to a unifying theory, there was evidence of a fifth--or anti-gravity--force. The article also related evidence of objects in free-fall being repulsed by a granite cliff.

As to the question of a bullet falling.... In a vacuum a bullet will return to earth at the same velocity as it went up. The gravitational force that slows an object going up (-9.8m/s^2) is the opposite (and equal) of it coming back down (9.8m/s^2) (both |9.8m/s^2|). Adding air resistancee back into the equation makes the math veeery complicated. What we do see though is that a smaller projectile (less surface area) will return at a rate closer to its initial velocity. Therefore, a .22 projectile comes closer to muzzle velocity than a .30 projectile.

GinSlinger

Mal H
January 2, 2003, 05:34 PM
Mike - I believe the article was "Searching for the Secrets of Gravity". The part you're talking about is some experiments performed by Ephraim Fischbach. It was reported in National Geographic, May, 1989.

It doesn't apply to falling bullets, at least not measurably.

faustulus
January 3, 2003, 01:36 AM
Mike,
I see your point about angle, and maybe that is my point. I think that many of these incidents that are reported every year are hits that occur not becuase someone was shooting at a 45 degree or less angle. Hence the bullet still retains much of its horizonal velocity while losing its vertical velocity.

Thanks for the articles, those were interesting. I will have to look up that national geographic article sounds like a must read.

4thHorseman
January 3, 2003, 02:32 AM
You guys have wwwaaayyy to much time on you hands. I sat here and read every post, so I guess must also.:D

Chugach
January 3, 2003, 03:15 AM
Just as a reality check, assume that a falling bullet can reach at least the same terminal velocity that a skydiver in tuck position can reach: 200 MPH. Now, convert to fps:

200 mi/hr x 1 hr/3600 seconds x 5280 ft/mi = 293.3 fps

[This sounds about right...60 MPH is equivalent to 88 fps, so 200 MPH is roughly 3 times 60 MPH or about 3 x 88 = 264 fps.]

Don't know about anyone else, but I don't want to be hit by ...anything at even the pokey speed of ~300 fps.

What speed in fps does a decent paintball gun launch a (semi-solid) paintball at? Ever been hit at close range by a frozen paintball?

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