The correct answer is: B. Law of Conservation of Linear Momentum
The law of conservation of linear momentum states that the total linear momentum of an isolated system remains constant. This means that the total mass times velocity of an object or system of objects cannot change, unless an external force acts on it.
When a gun is fired, the bullet is accelerated forward by the expanding gases from the gunpowder. This causes the gun to recoil backward, in accordance with the law of conservation of linear momentum. The total linear momentum of the system (the gun and the bullet) before the firing is zero. After the firing, the total linear momentum of the system is still zero, but now the bullet has a positive linear momentum and
the gun has a negative linear momentum of equal magnitude.The other options are incorrect because:
- Option A: The law of conservation of angular momentum states that the total angular momentum of an isolated system remains constant. This law does not apply to the recoiling of a gun, because the angular momentum of the system (the gun and the bullet) changes when the gun is fired.
- Option C: The conversion of kinetic energy to potential energy is a process that can occur in many different systems, but it does not apply to the recoiling of a gun. When a gun is fired, the kinetic energy of the gunpowder is converted into the kinetic energy of the bullet and the recoiling gun. However, the total energy of the system (the gun, the bullet, and the gunpowder) remains constant.
- Option D: The law of conservation of energy states that the total energy of an isolated system remains constant. This law does apply to the recoiling of a gun, because the total energy of the system (the gun, the bullet, and the gunpowder) remains constant. However, the law of conservation of energy does not explain why the gun recoils. The recoil of the gun is explained by the law of conservation of linear momentum.