CMC Medical CMC-Medical VELLORE Solved Paper-2010

  • question_answer
    At what height h above earth, the value of g becomes? \[\frac{g}{2}\] (R = Radius of earth)

    A)  3 R                                        

    B)  \[\sqrt{2}\]R

    C)  \[\left( \sqrt{2}-1 \right)R\]                       

    D)  \[\frac{1}{\sqrt{2}}R\]

    E)  None of these

    Correct Answer: C

    Solution :

                    The value of acceleration due to gravity at height h (when h is not negligible as compared to R) \[g=g\frac{{{R}^{2}}}{{{(R+h)}^{2}}}\] Here,     \[g=\frac{g}{2}\]                 \[\frac{g}{2}=g\frac{{{R}^{2}}}{{{(R+h)}^{2}}}\] or            \[\frac{1}{2}=\frac{{{R}^{2}}}{{{(R+h)}^{2}}}\] or            \[\sqrt{\frac{1}{2}}=\frac{R}{R+h}\] or            \[R+h=\sqrt{2}R\] \[\therefore \]  \[h=(\sqrt{2}-1)\,R\]


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