Laws Of Motion Question 32
Question: A rocket has a mass of 100 kg. 90% of this is fuel. It ejects fuel vapours at the rate of 1 kg/sec with a velocity of 500 m/sec relative to the rocket. It is supposed that the rocket is outside the gravitational field. The initial upthrust on the rocket when it just starts moving upwards is[NCERT 1978]
Options:
A) Zero
B) 500 N
C) 1000 N
D) 2000 N
Show Answer
Answer:
Correct Answer: B
Solution:
$ F=u( \frac{dm}{dt} )=500\times 1=500\ N $
