Deadly Force

[RPM]

Re: patrickg's stuff

An AK47 has a 7.62 mm round (.308) ... but I assume that anything would hurt. I doubt that the velocity / pain would be greater than if the projectile was picked up and thrown at the person though.

The terminal velocity can be solved using Stokes Law - but I can't remember how to do it off the top of my head - will have to rummage around a bit. Haven't played with fluid dynamics for a bit. Key assumption would be that the Mach number is less than 1 - i.e. bullets are not supersonic (they aren't - at least not in free fall). Assuming a sphere it would be pretty easy to pick out the drag coefficient - fairly simple changes in bullet geometry can alter the results for stable flight - but a sphere makes the math easier.

Re: precession etc. Precession implies a somewhat stable dynamic - or at least one on the edge of stability - but the bullet would actually be randomly tumbling. Spin stabilization would be lost / translated into rotation about other axes before free-fall occurred.

I'll see what I can dig up.

By the way, my name is Patrick too - how ironic!!

 

[patrickg]

To: Patrick
Fromatrick

Hi, Patrick, one of my favorite Einsteinian sayings is, "Everything should be made as simple as possible, but no simpler"

Therin lies the crux of the problem with assuming a spherical projectile because the math is easier. You convert the problem to one that is easy to understand but unfortunately does not model the original problem closely enough. For years and years Physicists studied two and even three body elastic (billiard ball sort of thing) collisions and described them thoroughly in mathematics. Wonderful, but with more "balls" it became just too hard.

I don't think the issue was, "given a spherical projectile...", it was real world bullets.

Next: Why do you say that there would be no spin on a bullet fired vertically by the time it stopped its upward motion? The force retarding spin is an aerodynamic skin friction that is a rotational velocity dependent viscous dampening. The slower the bullet rotates the less friction. Are you claiming that the vertically fired round will overcome both gravity and aerodymamic drag much more successfully than the spin will maintain in the face of its retarding force and the bullet will tumble before it hits its zenith? Fired horizontally and falling by gravity a bullet's aerodynamics cause a vertical lift component (asymetrical due to spin). This can initiate perturbations in the trajectory/tumbling. This is not an issue when fired vertically. I don't think it was sophistry and or artifice when I simplified the problem by firing vertically, rather it was following the earlier Einstein quote, but I think a real bullet fired vertically is a better analog that reductio ab adsurdum via assuming a spherical one.

Not that this isn't fun but... Instead of arguing about the number of angels dancing on the head of a pin why not take a loupe and count the buggers. Theory is fine but only as an aid to experiment not as an end unto itself. Actually I bought a 300 gal fuel tank on an 8 ft stand yesterday at an auction and I need to clean it out, replace the old hose/nozzle, and put some fuel in it so I can try it out. Really tired of fueling via plastic cans while standing on the front tire of the Kubota.

Patrick
Patrick

 

[JOR_EL]

PatrickG,

Assuming a question mark was intended, at the end of this sentence; [[[ Instead of arguing about the number of angels dancing on the head of a pin why not take a loupe and count the buggers.]]]

...here's my not-entirely-tongue-in-cheek suggestion for an answer;

Because, with the loupe, you may be able to plainly see that there ARE no angels, ...and reporting this (npc)fact will surely result in your being mired in the religious fanatic/disbeliever quagmire. Some things are more-popularly left unexamined!

/w3tcompact/icons/laugh.gif

Larry

 

[JOR_EL]

Hey, you Patrick guys!

Not to disparage "techno-fun" (precession, viscous-dampening and the like), nor to engage in "sophistry" or "artiface", or any such, ...here is another thought on the subject(simplified), i.e.; "Can a person be hurt/killed by a "falling" bullet, which has been fired vertically (or nearly so)?":

Let's go with Einstein (and Thoreau!) and "simplify".
If we choose to ignore the evidence of dead bodies resuting from "celebratory" or "warning" bullets(After all, they may not have been fired REALLY vertically!), then I suggest we argue the case using a "worst-case" scenario-- which argument, if sucessfull, will "simplify" things by making references to precession/orientation/spin etc., superfluous(my modest contribution to the impressive-word collection /w3tcompact/icons/wink.gif ).

I call your attention to my past EMPIRICAL "evidence" of the falling-skydiver example, with an accepted "ballpark" speed of 120 mph(176fps).

With the skydiver's configuration(basic-stable position, i.e. spread-eagled)/atitude(physical, not mental, i.e. horizontal)/surface (lumpy, irregular rough-textured, flapping) surely inferior to the most unstable bullet(re. aerodynamics), and a density 1/10 as great(or less), we may reasonably infer, I believe, that 400fps is a not-unreasonable estimate for a max vel. of the superior(terminal velocity-wise) missle(the lead bullet), when the same accelerating force(gravity) is applied., and the same resisting fluid medium (air) is encountered.

If (IF!) we accept this estimate, and if we acknowledge the vel. needed to inflict damage to a human( given in previous posts on this thread)as being in this general range, ...or even lower), ...then the proposition has been proven using the "worst-case" scenario, and consideration of the possible effects of optimized spin, orientation,etc., is uncalled-for, as they would certainly only FURTHER substantiate an already-drawn conclusion.

The "simplified" conclusion being that "A bullet the size of one of the larger hand/shoulder-arm calibers, falling from a ht. attainable from these weapons, can reasonably be expected to inflict injury or death on a human being, REGARDLESS of ithe optimization/lack-thereof of its "flight" characteristics!"

The only "fly in the ointment" would seem to me to be the question of the "attained ht." being sufficient to allow the needed acceleration to adequate "damage" velocity. I think the "empirical" observation/conclusion, reasonably rules out gryoscopic(and other such) effects as determinants!

In other words, "simple"-physics(apples and gravity) demonstrates that if there is sufficient time(ht.) for the subject-projectile to approach its "worst-case" terminal velocity, the subject-human is in trouble.

No "fancy-physics" called-for! /w3tcompact/icons/crazy.gif

Huh?

Larry

 

[patrickg]

Jor El, I do not agree with your attempt to "simplify"! B U T if rather than hearing "We experienced 100% mortality of the aquatic biota" you would rather hear that "all the fish died" then I truly believe (don't try this at home kids) that a large caliber (say Colt .45 auto) pistol rounds fired vertically would return to earth in excess of 400 FPS and if striking a person a direct blow on the brain box could kill them outright or deal them a serious and probably life threatening wound.

A colt .45 automatic will blow a fatal hole in your head (we're talking Consumer Reports Check Rated lethal first time - every time) at 500 FPS. Standard ballistics for the 45 ACP range from about 750 to 1000 FPS but can't kill you any deader.

I thought the reason this thread continued was the enjoyment of teasing out the minutia in either scientific terms or, shall we say, fantasy terms. If there is a need for pragmatic conscise, clear, commumicative discourse then I'm sorry for my heresy but I couldn't tell from the predeeding posts that this was the case as I couldn't detect a serious thread in the entire bolt. Although I wrote at times with tongue in cheek I stand behind any of my previous posts' technical content.

Patrick (In south central Oklahoma with an overhead 300 gallon fuel tank.)

 

[JOR_EL]

Patrick,

[[[I thought the reason this thread continued was the enjoyment of teasing out the minutia in either scientific terms or, shall we say, fantasy terms. If there is a need for pragmatic conscise, clear, commumicative discourse then I'm sorry for my heresy but I couldn't tell from the predeeding posts that this was the case as I couldn't detect a serious thread in the entire bolt. Although I wrote at times with tongue in cheek I stand behind any of my previous posts' technical content.]]]


Don't disagree at all, ...just have always thought "teasing" was a 2-way street. Are we now in a "questionable" zone re. the "enjoyment of..."?

Pragmatism not "needed". Not "forbidden" either.

The idea of simplification( as in "Einsteinian", donchaknow) was not introduced by me. I was just "playing" with it.

Don't think any part of this thread is "needed", ...just a sensayuma.

[[[I do not agree with your attempt to "simplify"]]]

Care to say just what it is, with which you disagree?

/w3tcompact/icons/smile.gif

Larry

 

[patrickg]

Larry et al, It must be the heat and my inability to use them cute lil emoticons, I seem to be taken seriously when I'm not and other difficulties. You guys carry on, I'm gonna sit on the sidelines for a while and keep score. I think I fried my brain Saturday standing for hours out in the sun during the heat of the day just to get a bargain on an overhead fuel tank. If it gets much hotter I might volunteer to be a test dummy for the vertical bullet test just to be put out of my misery.

Patrick in really H O T south central Oklahoma with a 300 gal overhead fuel tank.

 

[RPM]

Well ... did the calculations a couple of ways (and I'm not about to try and get all the calc's in here with all the Greek symbols tonight!)

Rough and ready (and I'm admittedly a bit rusty) - 1/2 inch lead sphere. Terminal velocity in free-fall (in air) will lie in the range of 130 - 210 feet per second.

The range is due to playing with variables regarding the drag coefficient (CD) and the kinematic viscosity of air at differing temps/pressures/altitudes.

I think it would give you a nasty bruise, possibly fracture your skull or knock you unconscious. If hit in the wrong spot it could kill - think David and Goliath! Definitely borderline though - not a sure thing. Some of us are certainly more hard-headed than others /w3tcompact/icons/smile.gif

Not that I plan to try this anytime soon - and I wouldn't recommend to others!!

Patrick

P.S. patrickg - I played with the spin idea. Some interesting differences arise for short (pistol) and long (rifle) barrels. Basically, you were right - the spin would last longer than the typical bullet flight. The net effect is that if you fire a bullet vertically up the spin will mean that on it's path down it will retain the same orientation as on the way up. In other words, it will fall with its flat end pointed to earth - and its curved end pointed up (for a normal looking bullet) - the same orientation as on the journey up.