The Physics of stray bullets

[gwattal]

A woman in the stands at the Cardinals-Brewers Tuesday was hit with a stray bullet shot from a location police believe was probably a mile away.

https://www.inverse.com/article/31220-f ... ll-stadium

[I Like Pie]

While my comment has nothing to do with the story, it does remind me of a passage from one of my favorite authors, Mark Twain. This particular passage was from a speech given in 1882 entitled, "Advice to Youth". It follows thusly,

"Don't meddle with old unloaded firearms. They are the most deadly and unerring things that have ever been created by man. You don't have to take any pains at all with them; you don't have to have a rest, you don't have to have any sights on the gun, you don't have to take aim, even. No, you just pick out a relative and bang away, and you are sure to get him.
A youth who can't hit a cathedral at thirty yards with a Gatling gun in three-quarters of an hour, can take up an old empty musket and bag his mother every time at a hundred.
Think what Waterloo would have been if one of the armies had been boys armed with old rusty muskets supposed not to be loaded, and the other army had been composed of their female relations. The very thought of it makes me shudder."

[mundaire]

The physics behind falling bullets causing injury has been discussed here earlier as well, see viewtopic.php?t=879

For those too lazy to check out the above link, the gist is as follows:

1. What goes up must come down - Simple enough, unless an object attains "escape velocity" (which is not the case here), it will return back to earth.

2. The bullets come down base first - This is aerodynamically stable for that shape without spin stabilisation, but many assert that it returns base first due to still being spin stabilised in a similar orientation to when it went up. Either way, it does come down base first.

3. Theoretically an object fired into the sky (at a perfect 90 degree angle) will come down with the EXACT SAME velocity with which it left the ground. But this is true only in a vacuum, which isn't the case here. Factors like air-resistance, wind velocity etc. will also be acting on the bullet. What we need to look at is something called terminal velocity. The bullet will leave the gun at a certain muzzle velocity; this multiplied by its mass will give you the figure for muzzle energy. Much of this energy will be dissipated by air resistance, some will be used up by the horizontal component of its flight path (a shot fired at a perfect 90 degree angle being rare) and the rest would be used up combating gravity.

Eventually the bullet will reach its maximum altitude, a point where its velocity is zero and begin "falling" back to earth. When something is falling, it reaches a terminal speed where the losses of energy caused by air friction equal the gain in energy through acceleration caused by gravity. This is the "Terminal velocity" of the bullet and is considerably slower than the original muzzle velocity of the bullet.

4. Even if a gun were fired at an angle of exactly 90 degrees, even relatively low wind speeds would cause the bullet to drift and the chances of it returning to the exact same point from where the gun is fired are remote. This has in fact been experimentally proven to be true.

5. The US Army conducted some experiments during the 1920s to determine the speed of falling bullets. They fired .30 calibre, 150 grain, Spitzer point bullets, at a velocity of 2,700 f.p.s. during these experiments. Based on the results of these tests it was concluded that the bullet return velocity was about 300 f.p.s. For the 150 grain bullet this corresponds to an energy of 30 foot pounds. Earlier the US 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 grain service bullet would not be lethal, although it could produce a serious wound.

The key to the US Army's determination of falling bullets as not having enough lethal force is based on the muzzle velocity, calibre & weight of the bullet, the exact angle at which the gun is fired, prevailing weather conditions, the angle at which the bullet strikes the victim and of course the exact area of the victims body that is struck.

From the above it is safe to conclude that given the right conditions; falling bullets can cause injury, in some cases serious injury and in rarer cases even death.

[goodboy_mentor]

The center of gravity of a free falling object decides which side of the object will fall first. Bullets come down base first because center of gravity of the bullet is located towards the base. Center of gravity is an imaginary point in an object where the total mass/ weight of the object appears to be concentrated.

Standard acceleration due to gravity is around 9.8 meters per second square. Higher the bullet goes up in the sky, gravity will get more time to accelerate it towards the earth. Thus higher the bullet reaches up in the sky before falling, higher will be it's downwards velocity when it hits the earth.

[Woods]

One rule of thumb almost always works for stray bullet - - if a bullet goes astray it finds an ar*e to sink in .
Population density is so high in india , plus there is a habit of spying on people plus there are always a number of people with " lotaa" in deserted place especially around sources of water . So watch out bros .

[ganeshn]

The center of gravity of a free falling object decides which side of the object will fall first. Bullets come down base first because center of gravity of the bullet is located towards the base. Center of gravity is an imaginary point in an object where the total mass/ weight of the object appears to be concentrated.

Standard acceleration due to gravity is around 9.8 meters per second square. Higher the bullet goes up in the sky, gravity will get more time to accelerate it towards the earth. Thus higher the bullet reaches up in the sky before falling, higher will be it's downwards velocity when it hits the earth.

a falling object is basically in a free fall, essentially there is no "experienced gravity" and hence no preferred orientation.as a thumb rule objects of different mass fall at the same rate.

[goodboy_mentor]

a falling object is basically in a free fall, essentially there is no "experienced gravity" and hence no preferred orientation.as a thumb rule objects of different mass fall at the same rate.

When the projectile is fired towards the sky, it reaches a point where it's velocity finally becomes zero and then starts downwards free fall. When the velocity is zero, at that point of time, projectile experiences gravity and center of gravity will play its role to tumble it towards the base. Isn't it? Moreover it is not a perfect free fall because of air resistance.

Yes of course standard acceleration due to gravity is not dependent on mass of the object, hence all objects regardless of their mass fall at same acceleration. Object that is comparatively higher up in the sky before falling, will be accelerated by gravity for more time, resulting in more final velocity when touching the ground. The formula will be Final Velocity = Initial velocity + Acceleration x Time

[mundaire]

No quite! On its way down, the object (bullet in this case) will keep accelerating till the point that the accelerating force exerted by gravitational pull is equal to the drag/ force of resistance of the medium through which it is falling (in this case air). Once these forces reach a point of equilibrium the object ceases to accelerate and continues falling at a constant speed called the terminal velocity.

Therefore, even if two different objects of equal size & shape leave the earth at significantly different velocities (muzzle velocity in this case) and therefore reach two very different altitudes, on their way down they will achieve equal (terminal) velocity.

This would be true, so long as both go high enough that on the way down they reach a point where accelerating force exerted by gravitational pull is equal to the drag/ force of resistance of air.

http://forensicoutreach.com/library/the ... -velocity/

A .30-06 rifle bullet, shot straight up with an initial velocity of 2,900 feet per second (880 m/s), will eventually lose all inertia. The top of the arc is too steep to crest and therefore — once the forward motion is dissipated — it will fall back to earth. It will again accelerate due to gravitational forces until drag from air resistance lets it reach terminal velocity on its unpredictable return path. Incidentally, the bullet fired upwards will not always come back down facing downwards.

Major General Julian Hatch, a U.S. Army firearms expert, did extensive testing on ballistics and falling projectiles in the 20’s. He calculated that .30 caliber rounds will reach terminal velocities of 300 feet per second (90 m/s) on descent, and determined that, while most bullets will leave a small dent in the ground when they land, that same bullet travelling between 200 to 330 feet per second can still penetrate human skin. The experience of many hospitalized and killed innocents validate his conclusions.

As you can see from the above, while on the way up the bullets initial velocity (muzzle velocity) is 2,900 feet per second, on the way down it is significantly lower at 200 to 330 feet per second.

[farhan.lateefi]

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