AMU Medical AMU Solved Paper-2005

  • question_answer
    The earth revolves around the sun in 1 yr. If distance between them becomes double, the new time period of revolution will be

    A)  \[4\sqrt{2}yr\]                                 

    B)  \[2\sqrt{2}yr\]

    C)  4 yr                                       

    D)  8 yr

    Correct Answer: B

    Solution :

                     From Keplers third law of planetary motion \[{{T}^{2}}=k\,{{R}^{3}}\] where T is time period and R the distance between earth and sun. \[\therefore \]  \[{{\left( \frac{{{T}_{1}}}{{{T}_{2}}} \right)}^{2}}={{\left( \frac{{{R}_{1}}}{{{R}_{2}}} \right)}^{3}}\] Given,   \[{{R}_{2}}=2R\],              \[{{R}_{1}}=R\] \[\therefore \]  \[{{\left( \frac{{{T}_{1}}}{{{T}_{2}}} \right)}^{2}}={{\left( \frac{1}{2} \right)}^{3}}=\frac{1}{8}\] \[\Rightarrow \]               \[\frac{{{T}_{1}}}{{{T}_{2}}}=\frac{1}{2\sqrt{2}}\] \[\Rightarrow \]               \[{{T}_{2}}=2\sqrt{2}\,{{T}_{1}}\] Given,   \[{{T}_{1}}=1yr\] \[\therefore \]  \[{{T}_{2}}=2\sqrt{2}\,yr\]


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