Deadly Force

[WVBill]

Check out this link. Might provide some info about how fast the bullet will be going when it comes down.

Although the weight and velocity don't match up with our bullet, it looks like it will be coming down as fast as it goes up.


http://www.phys.virginia.edu/classes/109N/more_stuff/Applets/ProjectileMotion/jarapplet.html

 

[JOR_EL]

Hey Harv, where can I get one of those "smarty" hats? /w3tcompact/icons/smile.gif

How about a small correction, ...since we're being "technical"?!

[[[ Eventually, the resistance of air friction reduces the acceleration to zero, leaving the object falling at a constant velocity (terminal velocity). ]]]

correction;" ...to zero, after which the object falls at a DIMINISHING velocity, as the ( standard conditions!) air density increases with decreasing altitude, therefore increasing resistive drag, and slowing the fall."

Re. the 130mph "terminal velocity" figure; Thinking way back to some younger sykdiving days, ...the accepted figure for a skydiver in the "basic stable" position ( slowest fall ) was about 120 mph, with some individual variation.

This figure increased with a "delta" or "diving" position, to some where between 150-180mph, if memory serves.

A "spent" bullet, fired vertically , If it fell from the 1000-2000 feet necessary for the skydiver to fall, in order to reach "terminal vel., would have accelerated to a speed greater than the diver, beacause of its considerably greater mass/surface(drag)area ratio. I think any "tumble" destreamlining would not come close to making up the difference.

Add to this the fact that the (rifle) bullet were to reach a height somewhat greater than this, and it would have more time to approach/reach ITS "terminal velocity" which would be greater than the fastest skydiver, simply due to their physical differences.

My guess would put the bullet at 300 mph or so (best "fall" orientation) which makes a convenient conversion from 60mph/88fps X5, or 440 fps.

There probably are some less-hard-headed among us that would not survive a point-on hit from a 1/3 -1/2 ounce projectile at 400+ fps. /w3tcompact/icons/shocked.gif !! (didn't the military have some free-fall 45 caliber anti-personnel "bomblets" to shower enemy troops with?- must be some studies/data on those!)

I'm betting on at LEAST a migraine /w3tcompact/icons/crazy.gif /w3tcompact/icons/mad.gif !!

Physics books nail all this stuff down, of course, and the actual figures may be somewhat different, but it's kind of fun "off-the-top-of your head"n'-it in a thread like this /w3tcompact/icons/laugh.gif

Some of these TBN "digressions" are the best!

Larry

ps: "Raining bullets" are only one of a delightful potpourri of hazards to be encountered courtesy of the nuts in the "Holy Lands". No thanks!

 

[GlueGuy]

<font color=blue>it looks like it will be coming down as fast as it goes up</font color=blue>

Oh contrare. I plugged in two sets of variables:

First set:

Initial velocity = 666 Meters per second (a bit over 2185 fps)
Angle = 90 (straight up)
Mass = 2Kg (one HEAVY bullet /w3tcompact/icons/smile.gif)

Results:

Max distance = 0 (look out below!)
Max height = 2209.83 M (7250 ft)
End velocity = 39.24 m/s (128 fps)
Total time = 72.78 seconds

Second set:

Initial velocity = 666 Meters per second (a bit over 2185 fps)
Angle = 90 (straight up)
Mass = 1 Kg (<font color=blue>still</font color=blue> one HEAVY bullet /w3tcompact/icons/smile.gif)

Results:

Max distance = 0 (look out below!)
Max height = 1191.44 M (3908.9 ft)
End velocity = 19.62 m/s (64.4 fps)
Total time = 70.61 seconds

Conclusion: Get to the real weight of a bullet (a lot less than a kilogram, but this tool won't go smaller), and the terminal velocity will be a lot less than a 1Kg projectile; And that will be a lot less than 64 fps (which is 43 MPH).

I played around some more and discovered that for angles >6 degrees, the terminal velocity is essentially the same. At < 6 degrees, the terminal velocity gets larger and larger (ballistics time).

Examples (I lopped off the fractional parts /w3tcompact/icons/smile.gif):

Angle = 6 degrees, TV = 19 m/s
Angle = 5 degrees, TV = 22 m/s
Angle = 3 degrees, TV = 52 m/s
Angle = 1 degree, TV= 239 m/s
Angle = .5 degree, TV = 386 m/s
Angle = .1 degree, TV = 592 m/s





The GlueGuy

 

[Bird]

<font color=blue>21 feet with a .45, one round every 2 seconds. . piece of cake. Not quite. It was Darn hard to do. Very few recrutes got all 10 rounds out before the second whistle.</font color=blue>

Steve, I never used a .45, but it is a piece of cake with a .38 revolver after you've done it at least every 6 months for fifteen years./w3tcompact/icons/laugh.gif And in later years, when we started using speed loaders, it was just downright simple./w3tcompact/icons/wink.gif And when I attended the FBI National Academy, they were rebuilding Hogan's Alley so we had to use the other ranges./w3tcompact/icons/frown.gif

Bird

 

[scruffy]

Bird, I will agree with you on the (my own paraphrase) practice makes perfect. It was common on the department(s) that I worked to fire an average 300 practice rounds per week. The rounds were all handloads, so you can imagine the differentiation you could find between rounds. Still, the repetitiveness was good training.
Yep, I too went through the FBI firearms training, but mine was attendance at a 3 day 'traveling' show...so to speak...along with its companion classroom training a week later. Good training (both) but hell on sleep. I was working a graveyard shift w/90 mile patrol route, FBI classes ran 8 to 5 daily-thirty miles away, college class ran 7 to 10 pm daily, work from 11M to 7:A.M.. Never saw a pillow or a bed the entire three day run both times. Can't say I remember seeing the patrol route on the third night either!

 

[JOR_EL]

GlueGuy,

Boy have you got my counter-intuitive alarm ringing. /w3tcompact/icons/shocked.gif

Risky business, contesting "air" stuff with an "alive" homebuilder /w3tcompact/icons/wink.gif but, ...a few observations. I don't know into WHAT you "plugged" the data, but I see no reference to resistance, only mass. As the old physics discussion usually goes, there's 2 kg. of feathers, ...then there's 2kg. of lead. We're not talking vacuum here. the density of the object is definitely an issue.

Re. your 1st set. If the TOTAL time includes the trip UP (we've been discussing only the trip down) could you break it down into up-time/down-time?

Your 7250' max ht. is coincidentally near the 7000' alt. that used to be "standard" jump for a 30sec. freefall, with an opening altitude +/- 2000ft.

Thats 5000 feet of "fall" in 30 sec. (=167fps or just under the anticipated 120mph/176fps. this is the AVERAGE, the lower starting speed and greater final speed included). And we're talking a human body,...something a little closer to a "feather" than a lead bullet is.

Bottom line, the human is falling FASTER than your 2kg bullet(not likely). And in truth, the bullet is not opening its chute at 2000ft, but is free to continue at the same MAX speed (if terminal vel. has been reached) or at an increasing speed(if not), for the final 2000 ft. or so, leaving it with an AVERAGE that should be higher than the human, and a FINAL that should be much greater.

I can't buy a 5lb. chunk of lead falling from 7250 feet with a max of 128 fps, ...Amazing!! /w3tcompact/icons/crazy.gif

Last point; [[[Conclusion: Get to the real weight of a bullet (a lot less than a kilogram, but this tool won't go smaller), and the terminal velocity will be a lot less than a 1Kg projectile]]] ..once again, depends on relative densities, and shape (clean vs dirty in "drag' terms)...true if the "projectiles" are simply scaled up/down, as the mass increases much faster than the size(which causes "form' drag or the surface area (upon which "skin-drag" acts).

Interesting discussion /w3tcompact/icons/laugh.gif !

Larry

 

[ERNIEB]

When I was stationed in Germany, Southern Bavaria, a nearby town, Rothenburg O.T had an annual celebration a part of which was a play. The play was a reenactment of a historical/mythical event. It seems the town was conquered and taken over by an army. After the battle the commander of the invading army had the mayor brought before him, and also ask for a glass of wine. A quick thinking townsperson found a huge mug(about 2 gals. I think) filled it with wine and gave it to the commander, no doubt hoping to put him in a good mood. Maybe sparing the town from being burned to the ground. The commander being no dummy himself, saw thru this, and tried to turn the tables. He slid the huge mug over to the mayor telling him if he could drink it all in one drink, the town would be spared. The mayor did and the town was saved. This became known as the "Miestertrunk".
The town contacted our unit and asked if we could supply gunfire for the siege part of the play. It was all pretty simple. We stood in a group outsde the back of the theater, and a guy would wave a white flag out of the window. This was our que to start shooting up in the air. A red flag was cease firing.
There was about ten of us, and the firing lasted for about 15 minutes. So how come nobody got hit by falling bullets? Simple, We were firing blanks. I suspect the Arabs are doing the same.
Off the track, but one thing I noticed from this odd exercise is that if you want to draw a crowd of people, just get a few people to fire weapons in the air. Every time we did this, by the time we were finished, we had hundreds of people gathered around us.

Ernie

 

[Harv]

WVBill -
The java applet on that page crashes my browser /w3tcompact/icons/frown.gif, and I'm too lazy to go into the next room and try it on one of my other systems.

As far as the bullet coming down as fast as it went up, that would only be true in a vacuum, so we'd have to go the moon to try that out. /w3tcompact/icons/smile.gif

JOR EL -
Yeah, it's been kind of fun trying to draw on memories from my college physics classes to reason this falling bullet thing out. I can see my physics books on the shelf about 6 feet from me, but that's too far right now (did I mention I'm lazy? /w3tcompact/icons/crazy.gif).

You're really picking nits with the increased air density thing, but you're absolutely right. /w3tcompact/icons/wink.gif

Oh, and the "smarty hat" is from my private wardrobe. I always recommend that we all stick to the emoticons that Muhammad provides, but sometimes I just can't help myself. /w3tcompact/icons/blush.gif

GlueGuy -
You've got that Silicon Valley approach to the problem. Almost makes me homesick for Corporate America. Almost. /w3tcompact/icons/tongue.gif

ErnieB -
The fellas I was referring to who were firing into the air, were frontline Iraqi soldiers. If they really were shooting blanks, as you suggested, it would certainly explain the outcome of that war, wouldn't it? /w3tcompact/icons/wink.gif

My head is starting to hurt, not so much from bullets landing on it, but from the depth of the science we have reached on this one. Can we just agree that firing into the air is a dumb idea? /w3tcompact/icons/crazy.gif

 

[skent]

Harv

Bravo! Good Deal!

Steve

 

[WVBill]

GlueGuy:

My mistake was that I ran the model with air resistance turned off.

Since we don't know what factor the designer used for air resistance in the model (a bullet or a blimp?), it's probably fair to say that we still don't know the true result for end velocity for a bullet.

I looked at the other models referenced on that web page and none seem to allow for the adjustment of air resistance.

Still left unresolved is what damage a bullet would do striking a person at any given speed. For reference here, think of a baseball game. A batter, struck by a 90 mph fastball (anywhere other than the head) does not suffer life-threatening injury.

Interesting discussion.