A 2-kg rifle that is suspended by strings fires a 0.01-kg bullet at 200 m/s. The recoil velocity of the rifle is about

Question

Quizplus · Accepted Answer

The law of conservation of momentum states that the total momentum before and after firing must be equal. Before firing, the momentum is zero. After firing, the momentum of the bullet and the rifle must cancel each other out. The momentum of the bullet is 0.01 kg * 200 m/s = 2 kg*m/s. Therefore, the rifle must have a momentum of -2 kg*m/s. The recoil velocity of the rifle is -2 kg*m/s divided by the rifle's mass (2 kg), which equals -1 m/s. The negative sign indicates the direction is opposite to the bullet's motion.

A 2-Kg Rifle That Is Suspended by Strings Fires a 0.01-Kg