JEE Main & Advanced Physics Gravitation / गुरुत्वाकर्षण Question Bank Kepler's Laws of Planetary Motion

  • question_answer
    A body revolved around the sun 27 times faster then the earth what is the ratio of their radii [DPMT 2002]

    A) 1/3      

    B)             1/9

    C)             1/27    

    D)             1/4

    Correct Answer: B

    Solution :

                    \[{{\omega }_{\text{body}}}=27{{\omega }_{\text{earth}}}\]             \[{{T}^{2}}\propto {{r}^{3}}\Rightarrow {{\omega }^{2}}\propto \frac{1}{{{r}^{3}}}\Rightarrow \omega \propto \frac{1}{{{r}^{3/2}}}\]\\[r\propto \frac{1}{{{\omega }^{2/3}}}\] Þ \[\frac{{{r}_{\text{body}}}}{{{r}_{\text{earth}}}}={{\left( \frac{{{\omega }_{\text{earth}}}}{{{\omega }_{\text{body}}}} \right)}^{2/3}}\]\[={{\left( \frac{1}{27} \right)}^{2/3}}=\frac{1}{9}\]


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