The Triumph Dolomite Club - Discussion Forum

Sat in the car this afternoon on the way home I was listening to the sound of people in the Middle East firing AK-47s into the sky (on the radio). As I usually do, I wondered where the bullets come down.

I sat down this evening to try to figure it out.

The muzzle velocity of an AK-47 is 710 metres per second.
The drag coefficient of a bullet is apparently .4
Air density I decided on 1.2 kgm3
frontal area of the 7.62mm calibre round is .000045m3
Gravity I decided was 9.98 m/s/s
and the mass of the bullet is 9.3 grammes.
The gun would be shot 5 degrees from the vertical

I figured that the bullet would fall to earth 22 seconds later, and around 885 metres away. The speed on impact is 175.14 m/s.
Am I anywhere near?

isn't g 9.81ms^-2

We normally take the universal gravitational constant to be 9.81m/s^2

Quite an interesting question, been a long time since I did anything like that (first year Engineering Maths!) - might have a go tomorrow.

I shan't spoil your fun by telling you there's a load of ballistics calculators that'll tell you exactly what you need to know though!

You lot must have too much time on your hands, thinking about muzzle velocity etc etc.

muzzle velocity is the speed that I would run if someone pointed a gun at me...

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Previous owner of 42 Dolomite shaped vehicles, 14 Sprints, 12 1850s, 8 1500s, 3 V8s, 3 Toledos and 2 SEs

actually if that was true muzzle velocity really wouldn't be very fast.....

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Previous owner of 42 Dolomite shaped vehicles, 14 Sprints, 12 1850s, 8 1500s, 3 V8s, 3 Toledos and 2 SEs

according to sciencetist weekly (uk edition) the a ak47 round would land 1357 metres away ,next tuesday at a speed of 142 m/s given the variations in temp and global warming factors and the fact that if somone farts really loud the earth would shift .0000000000.172mm/s per milligram of carbon spent by the aircraft that just went overhead.
this is dependant on a large truck driving south in the M3 at 47.5 mph at the same time.
oh and flushing the loo would alter the gravitational pull rendering this estimate useless.

I don't know much about Maths but I do know that in America someone fired a gun into the air and some distance away someone died from a gunshot wound. Using maths and s##t like that they actually worked out that the seemingly innocent gun firing into the air some way away actually caused the death so just make sure should you find yourself in Gaza over the next few days that you take cover from stray bullets falling from the air.

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Mark

1961 Chevrolet Corvair Greenbrier Sportswagon
1980 Dolomite Sprint project using brand new shell
2009 Mazda MX5 2.0 Sport
2018 Infiniti Q30

obviously doesn't like the word s##t!

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Mark

1961 Chevrolet Corvair Greenbrier Sportswagon
1980 Dolomite Sprint project using brand new shell
2009 Mazda MX5 2.0 Sport
2018 Infiniti Q30

S= ut + 1/2 at squared

8 years ago that would make some sense to me. But I pretty much stopped doing anything that even looked like algebra the second I left my last A-level maths exam. The formula looks familiar, but I can't remember what it does.

some people would say that webers are better.

S - distance
u = initioal velocity...
a = accelaration
t = time.....

You need to allow for bouyancy in air, air resistance of projectile, which is a comple function of speed, air resistance and shape.

Ballistics is highly complex and sometimes comes up in the physics news groups...people have published papers on it....

Its essentially non deterministic because of variations in atmospheric pressure accross the flight....

So you'd be hard pressed to get it down to the nearest metre and 10th of a second.

Jonners

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Note from Admin: sadly Jon passed away in February 2018 but his humour and wealth of knowledge will be fondly remembered by all. RIP Jonners.

Absolutely. But it's still an interesting way to while away an hour.