Recoil of a Gun Problems in Hindi Medium

Recoil velocity of gun is

What is the recoil velocity of a gun having mass equal to 5 kg if a bullet of 25 g acquiress the velocity of 500 m/s after from the gun ?

Why does a gun recoil on firing? Obtain an expression for recoil velocity of gun.

A gun fires a shell of mass 1.5kg with a velocity of 150m//s and recoils with a velocity of 2.5m//s . Calculate the mass of gun?