Q. A machine gun fires a bullet of mass $40\ g$ with a velocity $1200\ ms^{- 1}$ . The man holding it can exert a maximum force of $144\ N$ on the gun. How many bullets can he fire per second at the most
A) One
B) Four
C) Two
D) Three
Explanation
(d) $u =$ velocity of bullet
$\frac{dm}{dt} =$ Mass of bullet fired per second by the gun
$\frac{dm}{dt} =$ Mass of one bullet $(m_{B}) \times$ Bullets fired per sec $(N)$
Maximum force that man can exert $F = u\left( \frac{dm}{dt} \right)$
$\therefore F = u \times m_{B} \times N$
$\Rightarrow N = \frac{F}{m_{B} \times u} = \frac{144}{40 \times 10^{- 3} \times 1200} = 3$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.