Question

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

Answer 1

Law of conservation of momentum

According to the law of conservation of momentum, the total momentum of a system remains constant in the absence of any external force, that is momentum is neither created nor destroyed.

Explanation

1. The relation between kinetic energy and momentum can be given as,

$KE=\frac{p^2}{2m}$

where $KE$ is kinetic energy, $p$ is momentum, and $m$is mass.

2. Since momentum is constant, it can be said that $KE\propto \frac{1}{m}$.

3. Therefore, kinetic energy is inversely proportional to the mass of the body. In other words, the greater the mass, the smaller will be the kinetic energy and vice versa.

4. Since the bullet is lighter, it will have greater kinetic energy. Conversely, since the gun is heavier, it will have lesser kinetic energy.

Therefore, when a bullet is fired from a gun, the bullet will have greater kinetic energy.