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Bullets and steel

leftysergeant

Penultimate Amazing
leftysergeant
Joined
Jul 13, 2007
Messages
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I think this is a good example of how the speed and weight of a projectile, plus its structre, allow softer materials, like aluminum, to penetrate steel.

http://www.gunsnet.net/forums/showthread.php?t=293168

I dodn't know the forumlae for kinetic energy, but perhaps someone with better math skills could give us a comparison of the relative kinetic energy of a 757, compared to a 149 grain 7.62X54R round.
 
its KE = 1/2mv2
assuming a 2500fps velocity for the bullet i figure about 2800 joules KE

for the 767, 100,000kg going 500mph is about 2.5 million joules

the numbers above do not necessarily reflect the views and opinions of reality...ive been wrong before when i just start punching numbers into windows calculator



a major difference would be the fact that the bullet has a smaller area over which its transferring its energy to the steel
 
Bullet Energy to 500 yards in Foot Pounds

Distance (yds) |0 |50 |100 |150 |200 |250 |300 |350 |400 |450 |500
M44 |2439 |2202 |1983 |1781 |1597 |1427 |1271 |1129 |1002 |888 |785
M28 |2745 |2484 |2243 |2021 |1817 |1629 |1456 |1299 |1154 |1024 |908
M91/30 |2808 |2541 |2296 |2070 |1861 |1670 |1494 |1333 |1185 |1052 |933
M91 (Finnish) |2835 |2567 |2320 |2092 |1881 |1688 |1511 |1348 |1199 |1065 |944
M91 (Russian) |2672 |2417 |2181 |1964 |1764 |1580 |1412 |1258 |1117 |991 |878
http://7.62x54r.net/MosinID/MosinAmmo031.htm
 
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defaultdotxbe said:
Its KE = 1/2mv2
Assuming a 2500fps velocity for the bullet I figure about 2800 joules KE.

For the 767, 100,000kg going 500mph is about 2.5 million joules.

The numbers above do not necessarily reflect the views and opinions of reality...I've been wrong before when I just start punching numbers into windows calculator.



A major difference would be the fact that the bullet has a smaller area over which it's transferring its energy to the steel.
Click to expand...

Well, you beat me to the formula, but I can double-check your numbers for you.


Bullet (7.62x51mm NATO, a.k.a. .308 Winchester):

Source for specifications. (It's Wikipedia, for which I apologize. Guns are not my knowledge ares, and it's all I could find.)
mass = 9.50 grams = 0.0095 kilograms
velocity = 840 metres per second
bullet diameter = 7.82 mm = 0.00782 metres.

KE = 1/2mv2 = 1/2*(0.0095 kg)*(840 m/s)2 = 3,350 Joules.

Cross-sectional-area of .308 Winchester round = 1/4(pi)(diameter)2 = 1/4*(3.14)*(0.00782 m)2 = 0.000048 m2
KE per unit cross-sectional-area: (3,350 J)/(0.000048 m2) = 69.8x106 Joules/metre2, or 69. million Joules/m2.
(69.8 million (kilograms per second per second) per squear metre cross-sectional-area)



Plane (Boeing 767):

Source. (Note the part where it says "The results of the analysis were in-line peer reviewed by Drs. Bob Nickell and Bob Kennedy. Dr. Nickell is a world recognized expert in the dynamic analysis of structures and used fuel containers. Dr. Kennedy is a world renowned structural analyst. ")
weight (max. takeoff) = 450,000 pounds. For this analysis, I will reduce this by 50%, to 225,000 pounds. (Note that this is likely far too low to be realistic, so the final KE numbers will likely be lower than in real life.)
velocity = 350 miles per hour
Cross-sectional-area of a Boeing 767-400ER = 45.2 metres2Source (right hand column, near bottom of page 719)
1 pound force = 4.45 Newtons (weight)
1 Newton (weight) = 0.102 kilograms mass
Therefore, (225,000 lb)*(4.45 N/lb)*(0.102 kg/N) = 102,000 kg, approximately.​
1 mile = 1,609 metres
1 hour = 3,600 seconds
Therefore, (350 miles per hour) = (350 miles/hour)*(1,609 metres/mile)*(1/3,600 hours/second) = 156.43 m/s​

KE = 1/2mv2 = 1/2*(102,000 kg)*(156.43 m/s)2 = 1.25x109 Joules, or 1.25 billion Joules, not million, by my calculation.

KE per unit cross-sectional-area: (1.25x109 J)/(45.2 m2) = 27.6x106 Joules/metre2, or 27.6 million Joules/m2.
(27.6 (million kilograms per second per second) per square metre of cross-sectional-area.)


I also found this while searching for the mass of the Boeing 767[/ur]

ETA: Alright, I don't know whay that link at the bottom doesn't work. I copied it atraight out of the ddress bar, just like the others, and set it up in code wrap just like the others. And now I can't link back to it. Strange.
 
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leftysergeant said:
I think this is a good example of how the speed and weight of a projectile, plus its structre, allow softer materials, like aluminum, to penetrate steel.

http://www.gunsnet.net/forums/showthread.php?t=293168

I dodn't know the forumlae for kinetic energy, but perhaps someone with better math skills could give us a comparison of the relative kinetic energy of a 757, compared to a 149 grain 7.62X54R round.
Click to expand...
Flight 11 and 175 hit with an impact energy of 1300 and 2200 pounds of TNT.

The design impact of a 707 lost in the fog, and low on fuel, goind slow to land, was 187 pounds of TNT!

When you look at what kind of energy is required to cut a steel column, the aircraft impacts beat it by a bunch.

The WTC design for a 707 impact was only 187 pounds of TNT, it would enter slightly but with 7 to 11 times less energy than 9/11, the results would be very different. No you can see why the cores were damaged and plane parts passed through the building on 9/11. The engineers of the WTC expected an accident 707 impact to only cause local damage and small fires, and much would drop to the ground. They only expected injuries and death at the impact zone, not far into the building. On 9/11 the impacts damaged the core and cut off most of the escape routes.

It was the terrorists and the velocity squared that made 9/11 a bad day.
 
I think a much easier response is "How does water cut stone?" Water isn't very hard yet ask anyone who cuts marble and stone what they use.

How does a paper playing card cut through wood in a tornado? paper is not as strong as wood.

How does air blow a person over in a hurricane or tornado (or blow a house over for that matter)? Air is not as strong as people or houses.
 
Jonnyclueless said:
I think a much easier response is "How does water cut stone?" Water isn't very hard yet ask anyone who cuts marble and stone what they use.
Click to expand...

I don't know about stone, but in metal water-cutting, they put an abrasive substance in the water jet.
Just so you know. Incase a truther jumps on you for that niggling little detail, or something.
 
X, I think you are referring to abrasive jets which are for harder materials like metal. But I don't doubt that such an argument would be made by the same people who don't understand how velocity or surface area plays a role.
 
As an upate, it appears my initial conclusion of the jet having a reater kinetic energy per unit area than the bullet was wrong.
I forgot to square the diameter when calculating the cross sectional area of the bullet.
After correcting the error, it seems the bullet has a greater KE/m2 than the jet. Which makes sense, given that we're comparing a tinay mass at a very high speed versus a large mass at a (relatively) much slower speed. The higher velocity-squared bit has a large effect, and higher mass/m2 (2.26 kg/m2 for the jet vs. 198 kg/m2 for the bullet) makes it so.

Can anyone double-check my numbers to confirm?
 
Lefty,Many high-powered rifles have muzzle velocities that are 3000 feet per second or more. That's more than 2000 miles per hour.
 
Its like asking how does someone survive an electric shock of 100kv uttering a minor yelp of pain? (the answer being low amperage).

Its not just the speed at which something hits, the mass of that object, the intertia and its momentum are very important aswell.
 
peteweaver said:
Its like asking how does someone survive an electric shock of 100kv uttering a minor yelp of pain? (the answer being low amperage).

Its not just the speed at which something hits, the mass of that object, the intertia and its momentum are very important aswell.
Click to expand...

I`m assuming you`re talking to lefty because he`s the one trying to make the comparison. Right?
 
Kinetic Energy of a 7.62mm or 5.56mm round:

A really bad day if you are on the receiving end.
 
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