A bullet of mass 5g is shot from a gun of mass 5kg . The muzzle velocity of the bullet is 500m/s .What is the recoil velocity of the gun?

Data:
Mass of bullet = 5 g = 5/1000 = 0.005 kg
Mass of a gun = 5 kg
Velocity of bullet = 500 m/sec
Recoil velocity of the gun = ?
Solution:
Momentum of the system before firing = M x 0 + m x 0
= 0
Momentum of the system after firing = MV + mv
= (5) (V) + (0.005) (100)
= 5V + 0.5
Since,
Initial Momentum = Final Momentum
So,
5 V + 0.5= 0
5 V = - 0.5
V = - 0.5/5
V = - 0.1 m/sec
which is the required recoil velocity of the gun.