RAJASTHAN PMT Rajasthan - PMT Solved Paper-2010

  • question_answer
    The mass of the moon is\[\frac{1}{81}\] of the earth but its 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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