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Posted: 10/8/2003 11:07:26 PM EDT
What is the average terminal velocity of a bullet dropped from high altitude? Does anyone know?
Link Posted: 10/9/2003 6:56:20 AM EDT
[Last Edit: 10/9/2003 6:57:22 AM EDT by Snark1]
The average failed paratrooper not tucked tight with no chute at all showing (and probably screaming) will hit at 100 to 150 MPH depending on body mass and inclination. Given that a bullet is both smaller and denser would probably hit faster but my college physics says not by a huge amount. I think I see where you're going and I wish I had documented figures or an equation for you but I don't. I'm gonna bet no more than 250 to 300 MPH. What do you think? Have you done a search? That one scene in "The Mexican" would have us beleive the velocity is higher than I bet it is. BUT.....A 350 grain 45-70 would undoubtedly have a higher velocity than a 55 grain 5.56....
Link Posted: 10/9/2003 7:05:16 AM EDT
Darn it devl....there is external surface area to internal volume to consider. density....total weight, and to a much smaller degree.....shape! I hate it when people ask questions like this.......it keeps me awake. Some places to look might even involve artillary or mortar round impact times because mortar rounds are essentially free falling weights!!!!!! I wish People didn't ask stuff that awakens my obsessive compulsive evil twin.
Link Posted: 10/9/2003 7:16:05 AM EDT
[Last Edit: 10/9/2003 7:19:00 AM EDT by 00_buckshot]
BUT.....A 350 grain 45-70 would undoubtedly have a higher velocity than a 55 grain 5.56....
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Weight has nothing to do with how fast gravity pulls an object towards earth. All objects fall with the same acceleration (10 m/s/s). "Free-fall is a special type of motion in which the only force acting upon an object is gravity. Objects, which are said to be undergoing free-fall, do not encounter a significant force of air resistance; they are falling under the sole influence of gravity. Under such conditions, all objects will fall with the same rate of acceleration, regardless of their mass." So if you had that 350gr. 45-70 slug and you had a similiar shaped slug made out of plastic only weighing 25 grains and dropped them from 30,000 ft. at the same time guess what would happen? They would both strike the ground at exactly the same time. Isn't physics cool? I remember the first time I learned this was in junior high and it took me the longest time to finally accept it.
Link Posted: 10/9/2003 7:59:26 AM EDT
I read a test done on a 30.06 round fired straight up in the air. I think the army did it. Anyway, most of this is from memory. It came to it's apex at 9,000 feet, and returned at 120 miles an hour. They said it only left a 1/4inch dent in the cardboard it hit. If I find the article again, I will post it.
Link Posted: 10/9/2003 8:06:15 AM EDT
[Last Edit: 10/9/2003 9:46:34 AM EDT by Ridge]
That is true in a vacuum. It's a little more complicated than that because you have to consider air resistance or drag that is acting on the object. You can figure it out using the equation here. v=sqrt(2W/CdrA) W=wieght Cd=drag coefficient, .295 for a bullet r= air density A=frontal area. v=velocity I would have done it for you but I didn't know the density of air. [url]http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html[/url]
Link Posted: 10/9/2003 8:08:32 AM EDT
[Last Edit: 10/9/2003 8:10:19 AM EDT by Lockedon]
Originally Posted By 00_buckshot: Weight has nothing to do with how fast gravity pulls an object towards earth. All objects fall with the same acceleration [RED](10 m/s/s).[/RED]
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It's acctually 9.8 Meters/second/squared, in a vacuum....hehehe [}:D] Edited to add: Damn you Ridge! you beat me to it![:D]
Link Posted: 10/9/2003 9:01:06 AM EDT
Originally Posted By 00_buckshot:
BUT.....A 350 grain 45-70 would undoubtedly have a higher velocity than a 55 grain 5.56....
View Quote
Weight has nothing to do with how fast gravity pulls an object towards earth. All objects fall with the same acceleration (10 m/s/s). "Free-fall is a special type of motion in which the only force acting upon an object is gravity. Objects, which are said to be undergoing free-fall, do not encounter a significant force of air resistance; they are falling under the sole influence of gravity. Under such conditions, all objects will fall with the same rate of acceleration, regardless of their mass." So if you had that 350gr. 45-70 slug and you had a similiar shaped slug made out of plastic only weighing 25 grains and dropped them from 30,000 ft. at the same time guess what would happen? They would both strike the ground at exactly the same time. Isn't physics cool? I remember the first time I learned this was in junior high and it took me the longest time to finally accept it.
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This is very true. However, since Newton states that net F=MxA (net Force equals Mass times Acceleration), and the heavier slug would have a higher mass, then the heavier slug would indeed arrive at the point of impact at the same time but would cause far more damage than the plastic slug since it would impact with more force. The kinetic energy from the higher force would have to be dissipated on impact.
Link Posted: 10/9/2003 12:36:48 PM EDT
[Last Edit: 10/9/2003 12:38:11 PM EDT by Forest]
DevL: There is a chapter on this in [u]Hatcher's Notebook[/u] (by General Hatcher). Even photos of his 'test aperatus'. If you don't have the book I suggest you find one - very interesting book for those of us interested in Rifles and how they work. BTW the AR-15/5.56 is breifly mentioned (as in very experimental at the time). You can still find it on Amazon.com [i]Edited to Add[/i] Duh I didn't answer the questions. Ok I don't recall the value, but it wasn't terribly impressive.
Link Posted: 10/9/2003 1:30:04 PM EDT
I call serious BS on the '06 only leaving a dent in cardboard after a 9,000' free fall. In a vacuum, any projectile fired vertically will return to its original location with exactly the same velocity as it was originally launched at. In the atmosphere, terminal velocity depends solely on the drag coeficient of the falling body. Bullets have a very high sectional density and are quite aerodynamic, so they have the capability to pick up some pretty impressive velocities in a free fall. If you dropped a bullet from high enough, it WILL go supersonic at some point. Hell, back in the early space program, they would have dudes jump out of high altitude balloons at 80,000 feet in pressure suits, and they would break the sound barrier during part of their fall. As they descended into denser atmosphere, they would slow back down though. BTW, At sea level, acceleration due to gravity is 9.81 meters per second squared. 32.3 feet per second squared for those of you stuck on christian units. -Spaceman
Link Posted: 10/9/2003 2:04:41 PM EDT
Originally Posted By 00_buckshot:
BUT.....A 350 grain 45-70 would undoubtedly have a higher velocity than a 55 grain 5.56....
View Quote
Weight has nothing to do with how fast gravity pulls an object towards earth. All objects fall with the same acceleration (10 m/s/s). "Free-fall is a special type of motion in which the only force acting upon an object is gravity. Objects, which are said to be undergoing free-fall, do not encounter a significant force of air resistance; they are falling under the sole influence of gravity. Under such conditions, all objects will fall with the same rate of acceleration, regardless of their mass." So if you had that 350gr. 45-70 slug and you had a similiar shaped slug made out of plastic only weighing 25 grains and dropped them from 30,000 ft. at the same time guess what would happen? They would both strike the ground at exactly the same time. Isn't physics cool? I remember the first time I learned this was in junior high and it took me the longest time to finally accept it.
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That's not strictly true. We are talking terminal velocity in an ATMOSPHERE! Surface area to internal volume is germaine as is density. Given a constant acceleration what you said would be true in a VACUUM.
Link Posted: 10/9/2003 2:09:58 PM EDT
Originally Posted By Ridge: Cd=drag coefficient, .295 for a bullet
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[b][i]If[/b][/i] it's pointed in the correct direction.
Link Posted: 10/9/2003 8:23:35 PM EDT
[Last Edit: 10/9/2003 9:52:20 PM EDT by DevL]
So whats the drag coefficient for a bullet going backwards? Bet none of the bullet manufacurers ever though to measure that one eh?
Link Posted: 10/9/2003 9:34:29 PM EDT
ok, I know this is vauge, but I have heard of hand loaders loading bullets backwards for an application I cannot recall (lot of help there huh?) maybe pointed bullets in a tubular mag?
Link Posted: 10/10/2003 1:26:05 AM EDT
Originally Posted By SgtRed: ok, I know this is vauge, but I have heard of hand loaders loading bullets backwards for an application I cannot recall (lot of help there huh?) maybe pointed bullets in a tubular mag?
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38spl hollow base wadcutters were sometimes loaded backwards. It made for one hell of a hollow point load out of a snub nosed gun. Hoppy
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