NEET Physics NLM, Friction, Circular Motion NEET PYQ-NLM Friction Circular Motion

The force on a rocket moving with a velocity \[300\text{ }m/s\] is 210 N. The rate of consumption of fuel of rocket is:[AIPMT 1999]

A) 0.7 kg/s

B) 1.4 kg/s

C) 0.07 kg/s

D) 10.7 kg/s

Correct Answer: A

Solution :

Thrust force on the rocket

\[{{F}_{t}}={{v}_{r}}\,\left( -\frac{dm}{dt} \right)\] (upwards)

Rate of combustion of fuel

\[-\frac{dm}{dt}=\frac{{{F}_{t}}}{{{v}_{r}}}\]

Given, \[{{F}_{t}}=210\,N,\,\,{{v}_{r}}=300\,m/s\]

\[\therefore \] \[-\frac{dm}{dt}=\frac{210}{300}=0.7\,kg/s\]