Punjab Medical Punjab - MET Solved Paper-1999

  • question_answer
    If the mass of the earth is \[80\] times of that of planet and diameter is double that of planet and \[g\] on earth\[9.8\,\,m/{{s}^{2}}\]. Then, the value of \[g\] on the planet will be

    A) \[0.49\,\,m/{{s}^{2}}\]                  

    B) \[4.9\,\,m/{{s}^{2}}\]

    C) \[0.98\,\,m/{{s}^{2}}\]                  

    D) \[9.8\,\,m/{{s}^{2}}\]

    Correct Answer: A

    Solution :

    Mass of the earth\[{{M}_{e}}=80\,\,{{M}_{p}}\] Diameter of earth\[{{D}_{e}}=2\,\,{{D}_{p}}\] or radius of the earth\[{{R}_{e}}=2\,\,{{R}_{p}}\] Gravitational acceleration is                 \[g=\frac{GM}{{{R}^{2}}}\propto \frac{M}{{{R}^{2}}}\]or\[\frac{{{g}_{e}}}{{{g}_{p}}}=\frac{{{M}_{e}}}{{{M}_{p}}}\times {{\left( \frac{{{R}_{p}}}{{{R}_{e}}} \right)}^{2}}\]                 \[\frac{{{g}_{e}}}{{{g}_{p}}}=\frac{80\,{{M}_{p}}}{{{M}_{p}}}\times {{\left( \frac{{{R}_{p}}}{2{{R}_{p}}} \right)}^{2}}=80\times \frac{1}{4}=20\] So,          \[{{g}_{p}}=\frac{{{g}_{e}}}{20}=\frac{9.8}{20}=0.49\,\,m/{{s}^{2}}\]


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