The correct option is A −12.5 m/s
In the absence of external force on the system of (gun+bullet) along the x direction, conservation of momentum will hold.
Mass of gun, mgun=2 kg
Mass of bullet, mbullet=0.01 kg
Velocity of bullet vbullet=250 m/s
Momentum of n bullets fired from the gun:
Let the recoil velocity of gun be v
Final momentum of system will be:
From Eq. (i),
Here −ve sign represents that the gun will recoil along the −ve x axis.