Math, for the record:
M256 120mm smoothbore accelerates a 10 kg projectile to 1650 m/sec over a distance of 6.6m (L55 barrel is 55 calibers)
Where x is displacement:
x = 1/2 a * t^2
v = a * t
==> x = 1/2 v * t
==> 6.6m = 825m/sec * t
==> 0.008 = t
1650m/sec / .008 sec = a = 206,250 m/sec^2.
F= m a
Fp = 10kg * 206,250 m/sec^2 = 2,062,500 N
Equal and opposite reaction requires that same force
==>Fp = Ft
2,062,500 N / 69,000 kg = 29.89 m/sec^2
28.89m/sec^2 * .008 sec = 0.239 m/sec
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Too much math?
This is what it means.
Firing a modern M256 120mm smoothbore (M1A2 main gun, sometimes compared to an AC/2) imparts enough force on firing to accelerate a 69 ton tank to a velocity of twenty-three centimeters per second. Of course, this pretty much requires a frictionless surface, and the recoil path must pass through the center of mass of the tank. .
Now you want to talk torque firing said weapon several meters from the center of mass?
Edited by Vapor Trail, 26 January 2013 - 03:05 PM.