Question

A machine gun fires a bullet of mass $40g$ with a velocity $1200{ms}^{-1}$. The man holding it can exert a maximum force of $144N$ on the gun. How many bullets can he fire per second at the most?

• A. one
• B. four
• C. two
• D. three

Answer 1

Answer: (D)

three

Given,

Maximum force man can withstand $=144N$

Mass of each bullet $=40grams=.04kg$

Velocity of each bullet $=1200m/s$

Let 'n' be the number of bullets fired per second.

The force exerted by machine gun no man = change in momentum of n bullets coming out per second.

$F=nmv$

$\Rightarrow 144=n\left(0.04\right)\left(1200\right)$

$\Rightarrow n=3$