Question

A bullet is fired from a gun. Which will have greater kinetic energy: the bullet or the gun?

Answer 1

1. Law of conservation of linear momentum: It states that 'If the net external force acting on a system of bodies is zero, then the momentum of the system remains constant.'
2. When a bullet is fired from the gun there is no external force acting on the system hence momentum is conserved.
3. Kinetic energy$=\frac{1}{2}m{v}^2=\frac{p^2}{2m}$ where, $p=$ momentum and $m=$ mass.
4. From the above formula of kinetic energy, we can conclude that kinetic energy is inversely proportional to mass.
5. So the mass of a gun is greater than that of a bullet therefore kinetic energy of a bullet will be greater than the kinetic energy of the gun.

When a bullet is fired from a gun the kinetic energy of a bullet is greater than the kinetic energy of the gun because the mass of the gun is greater than that of a bullet.