BCECE Medical BCECE Medical Solved Papers-2006

  • question_answer
    In the first second of its flight, rocket ejects 1/60 of its mass with a velocity of 2400 \[m{{s}^{-1}}\]The acceleration of the rocket is :

    A)  19.6 \[m{{s}^{-2}}\]      

    B)  30.2 \[m{{s}^{-2}}\]

    C)  40 \[m{{s}^{-2}}\]        

    D)  49.8 \[m{{s}^{-2}}\]

    Correct Answer: C

    Solution :

    Thrust force on the rocket                 \[{{F}_{t}}={{v}_{r}}=\left( -\frac{dm}{dt} \right)\] or            \[ma={{v}_{r}}\left( -\frac{dm}{dt} \right)\] where \[{{v}_{r}}\] is the exhaust velocity of gases and \[-\frac{dm}{dt}\] is the mass of the ejected per unit time. Given, \[v=2400\,\,m{{s}^{-1}},-\frac{dm}{dt}=\frac{1}{60}\,kg/s\],                 \[m=1\,\,gk\] Substituting the values in above relation                 \[1\times a=2400\times \frac{1}{60}\] or \[a=40\,\,m{{s}^{-2}}\]


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