Manipal Engineering Manipal Engineering Solved Paper-2013

  • question_answer
    Escape velocity at surface of earth is\[11.2\,\,Km/s\]. Escape velocity from a planet whose mass is the same as that of earth and radius\[1/4\]that of earth, is

    A) \[2.8km/s\]                       

    B) \[15.6km/s\]

    C) \[22.4km/s\]         

    D)        \[44.8km/s\]

    Correct Answer: C

    Solution :

    At a certain velocity of projection the body will go out of the gravitational field of the earth and will never return to the earth, this velocity is known as escape velocity.                   \[{{v}_{e}}=\sqrt{\frac{2G{{M}_{e}}}{{{R}_{e}}}}\] Given,   \[{{M}_{e}}={{M}_{p}},\,\,{{R}_{p}}=\frac{{{R}_{e}}}{4}\] \[\therefore \]  \[\frac{{{v}_{p}}}{{{v}_{e}}}=\sqrt{\frac{{{M}_{e}}}{{{M}_{e}}}\times \frac{{{R}_{e}}}{{{R}_{e}}/4}}=\sqrt{4}=2\]                 \[\Rightarrow \,\,\,\,\,{{v}_{p}}\,=2{{v}_{e}}\,=2\times 11.2\]                        \[=22.4km/s\]


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