J & K CET Engineering J and K - CET Engineering Solved Paper-2009

  • question_answer
    A body is projected up from the surface of the earth with a velocity equal to \[\frac{3}{4}th\] of its escape velocity. If R be the radius of earth, the height it reaches is

    A)  \[\frac{3R}{10}\]

    B)  \[\frac{9R}{7}\]

    C)  \[\frac{8R}{5}\]

    D)  \[\frac{9R}{5}\]

    Correct Answer: B

    Solution :

    If body is projected with velocity \[(v<{{v}_{e}}),\] then height upto which it will rise, \[h=\frac{R}{\frac{v_{e}^{2}}{{{v}^{2}}}-1}\] \[v=\frac{3}{4}{{v}_{e}}\] (given) \[\therefore \] \[h=\frac{R}{\frac{v_{e}^{2}}{\frac{9}{16}v_{e}^{2}}-1}=\frac{9}{7}R\]


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