BCECE Engineering BCECE Engineering Solved Paper-2007

  • question_answer
    A body is orbiting around earth at a mean radius which is two times as greater as the parking orbit of a satellite, the period of body is

    A)  4 days                                 

    B)  16 days                               

    C)  \[2\sqrt{2}\] days          

    D)         64 days

    Correct Answer: C

    Solution :

    Key Idea: Parking orbit is a geostationary satellites orbit. From Keplers third law of planetary motion, the square of period of revolution (T) is directly proportional to cube of semi-major axis of its elliptical orbit (a), i.e., \[{{T}^{2}}\propto {{a}^{3}}\] Given, \[{{T}_{1}}=1\,day\]         (geostationary)                                 \[{{a}_{1}}=a,{{a}_{2}}=2a\]                 \[\therefore \]  \[\frac{T_{1}^{2}}{T_{2}^{2}}=\frac{a_{1}^{3}}{a_{2}^{3}}\]                 \[\Rightarrow \]               \[T_{2}^{2}=\frac{a_{2}^{3}}{a_{1}^{3}}T_{1}^{2}=\frac{{{(2a)}^{3}}}{{{a}^{3}}}\times 1=8\] \[\Rightarrow \]               \[{{T}_{2}}=2\sqrt{2}\,days\]


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