a bullet of mass 30 g. is fired from a pistol of 2.1kg at a velocity of 300 m/s calculate the recoil velocity of the pistol

Answer 1

Total momentum remains zero.
The recoil momentum of the gun therefore equals the forward momentum of the bullet.

Vbullet*0.030 kg = Vrecoil*2.1kg

Vrecoil = (0.030/2.1)*300 m/s = 4.3 m/s