Question

A machine gun fires a bullet of mass 40g with a velocity  1200ms^-1.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.

Answer 1

(d) : Suppose he can fire n bullets per second
Therefore, Force = Change in momentum per second

144 = n x ( 40/100) x (1200)

or n = (144 x 1000)/(40 x 1200)

or n = 3.