JIPMER Jipmer Medical Solved Paper-1996

  • question_answer
    The mass of the planet is \[\frac{1}{9}\]th of the mass of the earth and its radius is half that of the earth. If a body weighs 450 N on the earth, then it is weight on the planet would be:

    A)  100 N                                   

    B)  200 N                   

    C)  450 N                   

    D)         900 N

    Correct Answer: B

    Solution :

    Here: mass of planet \[{{M}_{p}}=\frac{{{M}_{e}}}{9}\] where \[{{M}_{e}}\]mass of earth is. weight of the body on earth \[{{w}_{e}}=450\,N\] radius of the planet \[{{R}_{p}}=\frac{{{R}_{e}}}{2}\] (where \[{{R}_{e}}\] is radius of earth) From the law of gravitation that weight of the body \[w=\frac{GMm}{{{R}^{2}}}\Rightarrow w\propto \frac{M}{{{R}^{2}}}\] Hence, \[\frac{{{w}_{e}}}{{{w}_{p}}}=\frac{{{M}_{e}}}{{{M}_{p}}}\times {{\left( \frac{{{R}_{p}}}{{{R}_{e}}} \right)}^{2}}\] or            \[\frac{450}{{{w}_{p}}}=\frac{{{M}_{e}}}{\left( \frac{{{M}_{e}}}{9} \right)}\times \frac{{{\left( \frac{{{R}_{e}}}{2} \right)}^{2}}}{R_{e}^{2}}\] so,          \[{{w}_{p}}=\frac{450\times 4}{9}=200N\]


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