NEET Sample Paper NEET Sample Test Paper-58

  • question_answer
    Ratio of escape velocity at earth \[({{v}_{e}})\]to the escape velocity at a planet \[({{v}_{p}})\] whose radius and mean density are twice as that of earth is:

    A) \[1:2~\]                        

    B) \[1:2~\sqrt{2}\]

    C) \[1:4\]                           

    D) \[1:\sqrt{2}\]

    Correct Answer: B

    Solution :

    [b]  \[g=\frac{GM}{{{R}^{2}}}\] \[M=\rho V=\frac{4}{3}\pi {{R}^{3}}\rho \] \[g=\frac{G}{{{R}^{2}}}=\frac{4}{3}\pi {{R}^{3}}\rho \] \[g=\frac{4}{3}\pi GR\rho \] \[\frac{{{V}_{e}}}{{{V}_{p}}}=\frac{\sqrt{2\frac{4\pi }{3}GR\rho R}}{\sqrt{2\frac{4}{3}\pi G{{R}_{p}}\rho {{R}_{p}}}}=\sqrt{\frac{{{R}^{2}}\rho }{R_{p}^{2}{{\rho }_{p}}}}\] \[\frac{{{V}_{e}}}{{{V}_{p}}}=\sqrt{\frac{{{R}^{2}}\rho }{{{(2R)}^{2}}2\rho }}=\frac{1}{2\sqrt{2}}\]


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