Question

When a machine gun of power P fires n bullets per second, each with kinetic energy E, then P equals

• A. nE
• B. n/E
• C. E/n
• D. n²E

Answer 1

The correct option is A

nE

Step 1: Given data

Power of machine gun is, $P$

No. of bullets fired per second is $n$

Kinetic energy of each bullet is $E$

Step 2: Calculating power

Power is given as,

$P=\frac{W}{t}$

where, $W$ is work done and $t$ is time.

According to the work-energy theorem, the work done equals the change in kinetic energy. Therefore,

$W=E$

Since there are $n$ bullets fired, the total work done will be,

$W=nE$

Therefore, power can be calculated as,

$$\begin{gathered} P=\frac{W}{t} \\ =\frac{nE}{1s} \\ =nE \end{gathered}$$

Hence, the correct option is (A)