Question

A machine gun fires a bullet of mass 40g with a velocity of 1200m/s =. 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

This question was posed to me in an internship interview.

The origin of the question is Laws of Nature in portion Laws of Motion of Engineering Physics I

Answer 1

The correct choice is (d) Three

To explain I would say: Let the maximum number of bullets than can be fired per second be n

Change in momentum of n bullets = nm(v-u) = n×(40(1200-0))/1000 = 48n kgm/s

As impulse = Change in momentum

Ft = 48n

n = Ft/48 = 3bullets/second.