JEE Main & Advanced Physics Gravitation / गुरुत्वाकर्षण Question Bank Acceleration Due to Gravity

  • question_answer
    Acceleration due to gravity on moon is 1/6 of the acceleration due to gravity on earth.  If the ratio of densities of earth \[({{\rho }_{e}})\] and moon \[({{\rho }_{m}})\] is \[\left( \frac{{{\rho }_{e}}}{{{\rho }_{m}}} \right)=\frac{5}{3}\] then radius of moon Rm in terms of Re will be               [MP PMT 2003]

    A)             \[\frac{5}{18}{{R}_{e}}\]   

    B)             \[\frac{1}{6}{{R}_{e}}\]

    C)             \[\frac{3}{18}{{R}_{e}}\]   

    D)             \[\frac{1}{2\sqrt{3}}{{R}_{e}}\]

    Correct Answer: A

    Solution :

                    \[g=\frac{4}{3}\pi G\rho R\] \[\Rightarrow \,\,g\propto \rho R\,\Rightarrow \,\frac{{{g}_{e}}}{{{g}_{m}}}=\frac{{{\rho }_{e}}}{{{\rho }_{m}}}\times \frac{{{R}_{e}}}{{{R}_{m}}}\]             \[\Rightarrow \,\,\frac{6}{1}=\frac{5}{3}\times \frac{{{R}_{e}}}{{{R}_{m}}}\,\Rightarrow \,\,{{R}_{m}}=\frac{5}{18}{{R}_{e}}\]


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