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 $



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