If the force on a rocket moving with a velocity of 300 m/sec is 345 N, then the rate of combustion of the fuel, is

 

If the force on a rocket moving with a velocity of 300 m/sec is 345 N, then the rate of combustion of the fuel, is 

(a) 0.55 kg/sec

(b) 0.75 kg/sec

(c) 1.15 kg/sec

(d) 2.25 kg/sec

[NEET 1995]

Force is equal to rate of change in momentum: \[ F = \frac{mv - mu}{\Delta t} \]

Fuel Mass Flow rate, $\frac{m}{\Delta t}=\dot{m}$ Initial velocity, $u=0$ $v=300 \; m/s$ \[ 345 = \dot{m} \cdot 300 \] \[ \dot{m} = \frac{345}{300} = 1.15 \]