Laws Of Motion Question 186
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 [CPMT 1971]
Options:
A) 550 N
B) 50 N
C) 250 N
D) 250 dyne
Show Answer
Answer:
Correct Answer: B
Solution:
u = velocity of bullet $ \frac{dm}{dt}= $
Mass thrown per second by the machine gun= Mass of bullet × Number of bullet fired per second
$ =10\ g\times 10\ bullet/\sec $
$ =100\ g/\sec \ =\ 0.1\ kg/\sec $
$ \therefore $ Thrust $ =\frac{udm}{dt}=500\times 0.1=50\ N $
