Haryana PMT Haryana PMT Solved Paper-2010

  • question_answer
    The mass of the moon is \[\frac{1}{81}\] of the earth but gravitational pull is -\[\frac{1}{6}\]of the earth. It is due to the fact that

    A)  the radius of the moon is \[\frac{81}{6}\] of the earth

    B)  the radius of the earth is \[\frac{9}{\sqrt{6}}\] of the moon

    C)  moon is the satellite of the earth

    D)  None of the above

    Correct Answer: B

    Solution :

                    Gravitational   pull   depends   upon   the acceleration due to gravity on that planet. \[{{M}_{m}}=\frac{1}{81}{{M}_{e}},\,{{g}_{m}}=\frac{1}{6}{{g}_{e}}\] \[g=\frac{GM}{{{R}^{2}}}\]                 \[\Rightarrow \]               \[\frac{{{R}_{e}}}{{{R}_{m}}}={{\left[ \frac{{{M}_{e}}}{{{M}_{m}}}\times \frac{{{g}_{m}}}{{{g}_{e}}} \right]}^{1/2}}={{\left[ 81\times \frac{1}{6} \right]}^{1/2}}\]                 \[\therefore \]  \[{{R}_{e}}=\frac{9}{\sqrt{6}}{{R}_{m}}\]


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