Question

A machine gun is mounted on a 2000 kg car on a horizontal frictionless surface. At some instant the gun fires bullets of mass 10 gm with a velocity of 500 m/sec with respect to the car. The number of bullets fired per second is ten. The average thrust on the system is

• A. 550 N
• B. 50 N
• C. 250 N
• D. 250 dyne

Answer 1

The correct option is B 50 N

u = velocity of bullet
$\frac{dm}{dt}$ = Mass thrown per second by the machine gun
= Mass of bullet $\times$ Number of bullet fired per second
$10g\times 10bullet/sec=100g/sec=0.1kg/sec$
$\therefore Thrust=u\frac{dm}{dt}=500\times 0.1=50N$