A 10gm bullet is fired from a 5kg rifle horizontally with a velocity of 500 m/s .Find the recoil velocity of the rifle.
Mass of bullet, m = 10 g = 0.01 kg
Mass of gun, M = 5 kg
Velocity of bullet, v = 500 m/s
Recoil velocity of the gun, V = ?
Initially the gun and bullet were at rest, so, the initial momentum of the system is, Pi = 0
After firing the momentum of the system = momentum of gun + momentum of bullet
=> Pf = MV + mv
=> Pf = 5V + (0.01)(500)
=> Pf = 5V + 5
By conservation of momentum,
Pf = Pi
=> 5V + 5 = 0
=> V = -5/5 = -1 m/s
Thus, the recoil velocity of the gun is oppositely directed with respect to the velocity of the bullet.
The speed of recoil of the gun is 1 m/s.