A) \[127.5\text{ }kg\text{ }{{s}^{-1}}\]
B) \[187.5\text{ }kg\text{ }{{s}^{-1}}\]
C) \[185.5\text{ }kg\text{ }{{s}^{-1}}\]
D) \[137.5\text{ }kg\text{ }{{s}^{-1}}\]
Correct Answer: B
Solution :
[b] Given: Mass of rocket \[(m)=5000\text{ }kg\] Exhaust speed \[(v)=800\text{ }m/s\] Acceleration of rocket \[(a)=20\text{ }m/{{s}^{2}}\] Gravitational acceleration\[(g)=10\text{ }m/{{s}^{2}}\] We know that upward force \[F=m(g+a)=5000(10+20)=5000\times 30\] \[=150000\text{ N}\] We also know that amount of gas ejected \[\left( \frac{dm}{dt} \right)=\frac{F}{v}=\frac{150000}{800}=187.5\text{ }kg/{{s}^{-1}}\]You need to login to perform this action.
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