urgent

Let M and m be the mass of the gun and bullet resp. Initially both gun and bullet are at rest. Therefore, initial momentum before fire of the system is zero.

Let after fire v and V be the velocity of bullet and gun resp.

Momentum of bullet after fire = m v

Momentum of gunafter fire = MV

Total momentum of the system after fire = mv + MV

A/C to law of conservation of momentum,

mv + MV= 0

or, V = - ( = mv / M )

Negative sign shows that gun will recoil .