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9th Class Science Force and laws of motion Question Bank Force and Laws of Motion

  • question_answer
    In a rocket, fuel burns at the rate of \[1\text{ }kg\text{ }{{s}^{-1}}\]. This fuel is ejected from the rocket with a velocity of\[60\text{ }km\text{ }{{s}^{-1}}\]. This exerts a force on the rocket equal to

    A) 6000 N           

    B) 60000 N                     

    C) 60 N   

    D)        600 N.            

    Correct Answer: B

    Solution :

    Here, rate of burning fuel, \[\frac{dm}{dt}=1kg{{s}^{-1}}\] Velocity of fuel ejection, \[v=60km\,\,{{s}^{-1}}=60000m{{s}^{-1}}\] Thrust \[=\frac{dm}{dt}\cdot v=1\times 60000=60000N\] Thus, force exerted on rocket is 60000N.


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