Question

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) 1

(b) 4

(c) 2

(d) 3

Answer 1

Correct option  (d) 3

Explanation:

Force exerted by machine gun on man's hand in firing a bullet = Change in momentum per second on a bullet or rate of change of momentum

= (40/1000) x 1200 = 48 N

Force exerted by man on machine gun = Force exerted on man by machine gun

 = 144 N

Hence, number of bullets tired = 144/48 = 3.