Q. A gun fires bullet each of mass 1 g with velocity of ${10\ ms}^{- 1}$ by exerting a constant force of 5 g weight. Then the number of bullets fired per second is (Take $g = {10\ ms}^{- 2})$
A) 50
B) 5
C) 10
D) 25
Explanation
(b) Mass of each bullet$(m) = 1\ g = 0.001\ kg$
Velocity of bullet $(v) = 10\ {ms}^{- 1}$
Applied force $(F) = 5\ g$-wt.
$= \frac{5}{1000} \times 10\ N$
$= 0.05$ N
Let $n$ bullets are fired per second, then
Force= rate of change of linear momentum
$ie,\ \ F = n \times mv$
$\therefore$ Number of bullets fired per second
$n = \frac{F}{mv}$
$= \frac{0.05}{0.001 \times 10} = 5$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.