A machine gun fires 360 bullets per minute. Each bullet moves with a velocity of 600 ms^–1. If the power of the gun is 5.4 kw, the mass of
each bullet is,

Given,

Number of bullets n = 360

Power P = 540 watt 

Let m be the mass of a bullet,

The kinetic energy generated by 360 bullets,

$$\begin{gathered} KE=n\times \frac{1}{2}m{v}^2 \\ KE=360\times \frac{1}{2}\times m\times {600}^2 \\ KE=648\times {10}^{5}mJ \end{gathered}$$

We know that,

$Power=\frac{Kinetic Energy}{time}$

substituting the values,

$$\begin{gathered} 5400=\frac{648\times {10}^{5}m}{60} \\ m=5\times {10}^{-3}kg \\ m=5 gram \end{gathered}$$

Hemce the correct answer is 5 gm.