Deadly Force

Harv · May 9, 2001

WVBill -

Just to keep the argument alive -- a bullet falling from the sky is most likely to hit someone in the head, which as you point out is the one place you don't want a fastball to hit you, either. (Okay, there's two places -- batters wear a helmet and a cup! /w3tcompact/icons/shocked.gif).

Also, there's the ol' surface area thing. The 90 MPH impact of a baseball would be spread over a much larger area than a bullet. Think about pushing somebody with the head of a baseball bat. Then think about pushing them with the same force, using a sharpened pencil. Ouch!!!

Of course, to get technical about it, (which we seem hell-bent on doing here /w3tcompact/icons/wink.gif), the baseball, with it's larger mass, would have a lot more force behind it than a bullet with the same velocity.

I think this thread is becoming more lethal than any falling bullet. /w3tcompact/icons/laugh.gif

JOR_EL · May 9, 2001

ErnieB,

[[[ So how come nobody got hit by falling bullets? Simple, We were firing blanks. I suspect the Arabs are doing the same. ]]]

Nice thought, ...maybe! /w3tcompact/icons/crazy.gif

But that's a lot of judgement to ask of some of the 14 yr. old fanatics we've seen waving automatic rifles and itching for a chance to shoot, up-in-the-air included. And if we're talking "front-line soldiers", these are the kids that grow up to become some of them.

I think its just a cultural thing, and I don't think the average Joe over there buys a supply of blanks to load up when its "celebration time".

Neither do some of us, now that I think of it, ...I'm sure not all of the "reports" I hear on the forth of July/New Years are firecrackers! /w3tcompact/icons/shocked.gif

Larry

GlueGuy · May 9, 2001

Jor_el
To get those numbers I was using the applet that WVBill mentioned here. I just typed in the various parameters that it allowed. Problem is, it was dealing with a "projectile" with a minimum mass of 1Kg.

I'm not vouching for the accuracy of this little calculator, just reporting on what it says.

Some of the other calulators on the net allow you to plug in different altitudes (which would allow a variable air density). However, they got into minutia that I felt were going too far into the mud.

I still believe that a falling bullet would (at least) hurt like hell (can I say that here?), and maybe even kill or maim. You're not going to see me trying to find out.... /w3tcompact/icons/smile.gif

Harv
Right attitude. /w3tcompact/icons/smile.gif

The GlueGuy

JOR_EL · May 9, 2001

GlueGuy,

A further look at the "skydiver"(180#) vs the "2kg projectile"(5#) version of the falling-bullet question; /w3tcompact/icons/smile.gif

Using these good-enough-for-govt.-work figures, lead = 600#/cu.ft.(rounded), human = 60#/cu.ft [because some humans sink -others float, ... this puts the "average human" right around the 60#/cu.ft(rounded) figure for water.];

Putting both volumes(for a 180# human and 5# of lead) into cubic form for simplicity of math, and similar aerodynamics);

Orienting both for a 1-face-"flat" fall, to simplify drag calculations;

The human block has (+/-)1.25X the skin drag for each lb. of weight.
The human block has (+/-)1.41X the form/profile drag(frontal area) for each lb. of weight.

The 5# lead block "projectile", having less drag for each lb. of weight WILL fall faster than the human block!! /w3tcompact/icons/shocked.gif

The human falls (actually faster-than, in a "block" shape) 176fps.
The falling lead "projectile" is faster still, quite-likely by a large margin.

128fps for a 2kg "projectile" simply does not compute,...unless you use a computer, of course /w3tcompact/icons/wink.gif. The empirical evidence does not support the result.

This being the case, with the "1st set" as the given example, I would hesitate to put faith in any other "computed" answers re. smaller projectiles (real bullets), etc., until this apparent discrepancy is understood.

Corrections/comments welcome! /w3tcompact/icons/laugh.gif

Larry

JOR_EL · May 9, 2001

Hey Harv,

You're confusin' me, man; /w3tcompact/icons/shocked.gif

[[[Can we just agree that firing into the air is a dumb idea?]]]

[[[Just to keep the argument alive --]]]

So are we havin' fun yet? ...or are we bored?

One man's opinion -- I enjoy these brain-teasers with such a wide background-ed / far-flung group. ...definitely not conversations you can have just anywhere. Tunin'-out's an easy option, if interest wanes /w3tcompact/icons/wink.gif .

I use these trivia-breaks to give myself a rest, when the physical work gets me down for awhile! (Funny, ...doesn't seem to take as long as it used-to! /w3tcompact/icons/tongue.gif )

/w3tcompact/icons/smile.gif Larry

Anonymous Poster · May 9, 2001

Glueguy,

I noticed in your calculations for a 2 kg bullet(object?) and 1 kg bullet that the velocity was the same (666 m/s). Yet, I notice that the 2 kg bullet goes to a Max height = 2209.83 M (7250 ft) and the 1 kg goes to a Max height = 1191.44 M (3908.9 ft).

My thoughts are that the lighter object/bullet should go higher than the heavier one, given that they both have the same initial velocity of 666 m/s. I am not sure why this is occuring. Perhaps there is an error in the calculations of the model.

In high-school physics class, I always understood that if you halved the mass and the initial velocity was the same the object would go twice as far/high as the heavier one, all things being kept the same.

just curious,

Peter

JOR_EL · May 9, 2001

Hi Peter,

Think of hitting two objects straight up with a ball-bat.
A baseball, ...and a ping-pong ball. Which one do you think will go higher.

A lot of "physics" class discussion has the old "in a vacuum" tucked-in the equation somewhere, and ouside of theory, it is very often impossible to see that "all things" are "kept the same".

If two objects are travelling at the same speed, but one is much heavier thsan the other, the heavy one will have much more energy (momentum) going for it. There are situations where a heavier-bullet retains more energy, and is therefore better-able to overcome air-resistance (drag) at longer ranges, thereby maintaining its velocity better, and extending its range.

Physics texts, artillary manuals, and ballistics books for handloaders have some really interesting data on all this stuff. A lot of the facts are surprising, and make you think more than "twice".

/w3tcompact/icons/smile.gif

Larry

gerard · May 9, 2001

eastern state law is base on the retreat doctrine, meaning that one is required to retreat from an flight, if you will, if it is reasonably do so safely, even in your own house. Actually at least in NY this is not true. It is also not true that you can only use DPF to protect your life or someone elses. There are actually many situations in NY (which is a very restrictive state) where DPF is authorized though too complicated to go into detail here. Preventing/terminating a burglary of a residence IS authorized and you DO NOT have to retreat. In the texas cases cited the shooting in the store WOULD have been justified, the one to prevent the chicken theft would NOT have been justified unless the theives use physical force against the owner at which point it becomes a robbery and not a larceny. Gets complicated

GlueGuy · May 9, 2001

First, don't confuse these as my calculations! I was merely reporting the results from a simple java calculator that WVBill supplied.

However, you may be mixing initial velocity with initial energy input. It will take twice the energy to accelerate 2Kg to 666 m/s than it will to accelerate 1Kg. So the 2Kg projectile starts out with twice the energy, and thus momentum.

What's less clear is the effect of gravity and wind resistance. A 2Kg balloon going 666 m/s is going to slow down a lot faster than 2Kg of plutonium (for example) because of muych larger air resistance. I have no idea what the size/shape assumptions of this calculator presume, and there's no way to input that kind of data. The programmer may have assumed bullet shape, cube, sphere, who knows? At any rate the size/shape of the projectile would have a potentially huge effect on the actual results.

The GlueGuy

ERNIEB · May 9, 2001

While it may seem ludicrous that blanks are being fired, It really isn't. Blanks have a military use, just as, oh say tracers. Most military combat units, regardless of nationality would have at least access to at least some blanks.
I've never even set foot in the middle east, but I'll bet a dollar to a doughnut hole "frontline" Iraqi soldiers are able to obtain blanks. Same-same for Palestinian soldiers, or the Taliban.
Small groups, or splinter groups would be something different.
If he wanted them, I'm pretty sure Bin Laden could afford to buy a few blanks.

Ernie