A machine gun fires a bullet of mass 40, g with a velocity 1200, ms^{-1} . man holding it

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4-1.Newton's Laws of Motion

easy

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

A$1$

B$4$

C$2$

D$3$

Solution

Given : $m=40 \mathrm{g}=0.04 \mathrm{kg} \quad v=1200 \mathrm{m} / \mathrm{s} \quad F=144 \mathrm{N}$
Let $n$ be the number of bullets that can be fired per second. The force exerted by man must balance the change in momentum of the bullets per second.
$\therefore \quad F=m n v$
OR $144=0.04 \times v \times 1200 \quad \Longrightarrow n=3$ bullets per second

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