JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2013

  • question_answer
        Escape velocity at surface of earth is \[11.2km{{s}^{-1}},\]escape velocity from a planet whose mass is the same as that of earth and radius 1/4 that of earth is

    A)  \[2.8\text{ }km{{s}^{-1}}\]                         

    B)  \[15.6km{{s}^{-1}}\]

    C)  \[22.4\text{ }km{{s}^{-1}}\]                       

    D)  \[44.8\text{ }km{{s}^{-1}}\]

    Correct Answer: C

    Solution :

                    Escape velocity at earth is given by \[{{v}_{e}}=\sqrt{\frac{2G{{M}_{e}}}{{{R}_{e}}}}\] Given,  \[{{M}_{e}}={{M}_{p}},{{R}_{p}}=\frac{{{R}_{e}}}{4}\] \[\therefore \]  \[\frac{{{v}_{p}}}{{{v}_{e}}}=\sqrt{\frac{{{M}_{e}}}{{{M}_{e}}}\times \frac{{{R}_{e}}}{{{R}_{e}}/4}}\]                 \[=\sqrt{4}=2\]                 \[{{v}_{p}}=2{{v}_{e}}\]                 \[=2\times 11.2\]                 \[=22.4\,km{{s}^{-1}}\]


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