Question

If the force on a rocket moving with a velocity of 300 m/s is 210 N. Then the rate of fuel combustion is:

• A. 0.7 kg/s
• B. 1.4 kg/s
• C. 2.8 kg/s
• D. 10.7 kg/s

Answer 1

Answer: (A)

0.7 kg/s

$F=\frac{d}{dt}\left(mv\right)=v\frac{dm}{dt}$

$\Rightarrow$ $210=300\times \frac{dm}{dt}$

$\Rightarrow$ $\frac{dm}{dt}=0.7kg/s$