Question

Which law of motion is primarily involved during the gun recoil?
(A) First law
(B) Second law
(C) Third law
(D) Cannot determine

Answer 1

Hint
The recoil in a gun is caused due to the forward momentum of the bullet. The force with which the bullet is fired is balanced by the recoil of the gun. So the recoil follows Newton’s third law of motion.

Complete step by step answer
The word recoil means moving backward due to the impact of some kind of force.
Now in the case of a gun when a bullet is discharged, there is a backward thrust that is generated on the gun. This is because the bullet and the exhaust gasses gain a forward momentum. Now from the law of conservation of momentum, this forward momentum of the bullet is balanced by the backward thrust that is produced on the gun. The larger is the bullet, the more is the recoil on the gun.
So for the force with which the bullet moves forward, there is an equal and opposite force that causes the gun to recoil backwards. So hence this follows on the lines of Newton’s third law, which states that, for every action, there is an equal and opposite reaction.
Therefore, the gun recoil follows Newton’s third law of motion.
So the correct option will be (C).

Note
In the case of heavy machine guns, the recoil momentum is huge. This momentum is transferred to the ground with the help of the mounting platform on which the gun is installed. We can calculate the amount of recoil in a gun by the law of conservation of momentum, where the momentum of the bullet will be equal to the mass times recoil velocity of the gun.