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

Answer: (B)

50 N

Answer 2

u = velocity of bullet

$\frac { d m } { d t } =$Mass thrown per second by the machine gun

= Mass of bullet × Number of bullet fired per second

$= 100 \mathrm {~g} / \mathrm { sec } = 0.1 \mathrm {~kg} / \mathrm { sec }$

$\therefore$ Thrust $= \frac { u d m } { d t } = 500 \times 0.1 = 50 \mathrm {~N}$