A rifle of mass 2 kg is suspended by strings. The rifle fires a bullet of mass 1/100 kg at a speed of 200 m/s. The recoil velocity of the rifle is about

Question

Quizplus · Accepted Answer

The recoil velocity of the rifle can be calculated using the principle of conservation of momentum. Before firing, the total momentum of the system (rifle + bullet) is zero because neither is moving. After firing, the momentum of the bullet is its mass times its velocity, (1/100 kg) * (200 m/s) = 2 kg*m/s. For momentum to be conserved, the momentum of the rifle must be equal and opposite to this, so -2 kg*m/s. The mass of the rifle is 2 kg, so its velocity must be -2 kg*m/s divided by 2 kg, which equals -1 m/s. The negative sign indicates direction, so the magnitude of the recoil velocity is 1 m/s.

A Rifle of Mass 2 Kg Is Suspended by Strings