Question

A machine gun of mass 10 kg fires 20 g bullet with the speed of 500 m/s. If the necessary force is 100N to hold the gun in position, find the number of bullets fired per second.

Answer 1

The gun of mass 5 kg force change the bullet's momentum from zero (initially at rest ) to the final value of
Pf = mv = (20 / 1000) * 500 = 10kg m/s
time taken = x bullets are fired per sec

Force = dp/dt = 10x
=> 10x=100
So, the number of bullets is 10 bullets per sec.