Question

Recoil of a gun is an example of which principle?

• A. Conservation of mass
• B. Conservation of energy
• C. Conversion into kinetic energy
• D. Conservation of linear momentum

Hint:

Think about total momentum of the gun and bullet system before and after firing.

Answer 1

The Correct Option is D

Let us solve this with real numbers instead of just theory.

1. Suppose a bullet of mass 0.01 kg leaves the gun at 200 m/s.
2. Suppose the gun has a mass of 4 kg.
3. Momentum given to the bullet is \(0.01 \times 200 = 2\) kg m/s in the forward direction.
4. Since total momentum of the system must stay zero, the gun must get 2 kg m/s of momentum in the backward direction. Its recoil speed is \(v = 2 / 4 = 0.5\) m/s.
5. Check: total momentum after firing is \(2 - 4 \times 0.5 = 2 - 2 = 0\), same as before firing. This confirms momentum is conserved.

This numeric check shows directly why the gun moves backward slowly while the bullet moves forward fast, and it shows the law at work is conservation of linear momentum, not mass or energy conservation alone.