Question

If force on a rocket having exhaust velocity of 300 m/sec is 210 N, then rate of combustion of the fuel is

• A. 0.7 kg/s
• B. 1.4 kg/s
• C. 0.07 kg/s
• D. 10.7 kg/s

Answer 1

Answer: (A)

0.7 kg/s

Answer 2

$F = u\mspace{6mu}\left( \frac{dm}{dt} \right)$ ⇒ $\frac{dm}{dt} = \frac{F}{u} = \frac{210}{300} = 0.7\mspace{6mu} kg/s$