RAJASTHAN PMT Rajasthan - PMT Solved Paper-1997

  • question_answer
    Imagine a meteroid revolving around a big star in a circular orbit of radius R with time period T. If the force of attraction between star and meteroid is proportional to\[{{R}^{-5/2}},\] then T2 will be proportional to:

    A) \[{{R}^{3}}\]                      

    B)        \[{{R}^{7/2}}\]                  

    C) \[{{R}^{5/2}}\]                  

    D)        \[{{R}^{3/2}}\]

    Correct Answer: B

    Solution :

    Gravitational force is equal to centripetal force \[\frac{GMm}{{{R}^{5/2}}}=\frac{m{{\upsilon }^{2}}}{R}\] \[{{\upsilon }^{2}}=\frac{GM}{{{R}^{3/2}}}\] Time period \[{{T}^{2}}=\frac{4{{\pi }^{2}}{{R}^{2}}}{{{\upsilon }^{2}}}=\frac{4{{\pi }^{2}}{{R}^{2}}}{GM}\times {{R}^{3/2}}\]                 \[=\frac{4{{\pi }^{2}}{{R}^{7/2}}}{GM}\]                 \[{{T}^{2}}\propto {{R}^{7/2}}\]


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