Find out the recoil-velocity of the gun:
As shell of mass 200 gm is fired at a velocity of 50 metres/second by a gun of mass 20 kg. Find out the recoil-velocity of the gun.
Since initially shell and gun both are at rest
mg Vg (2) + ms Vs (1) = 0
∴ Vg (2) = recoil of gun = - (ms Vs (2) )/mg
= (0.2 × 50 )/20
= - 0.5 m / sec.
Negative sign defined that the gun moves in a direction opposite to that of the shell since reaction on the gun is along opposite direction to the motion of shell.