JCECE Engineering JCECE Engineering Solved Paper-2011

  • question_answer
    By what percent the energy of a satellite has to be increased to shift it from an orbit of radius\[r\]to\[3r\]?

    A) \[22.3%\]                            

    B) \[33.3%\]

    C) \[66.7%\]                            

    D)  \[100%\]

    Correct Answer: C

    Solution :

    Binding energy of satellite in 1st case                 \[{{U}_{1}}=\left( -\frac{GMm}{r}+\frac{1}{2}\frac{GMm}{r} \right)\]                      \[=\frac{GMm}{2r}\] Binding energy of satellite in 2nd case                 \[{{U}_{2}}=-\left[ -\frac{GMm}{3r}+\frac{1}{2}\frac{GMm}{3r} \right]=\frac{GMm}{6r}\] Energy increased                 \[\Delta E={{U}_{1}}-{{U}_{2}}\]                       \[=\frac{GMm}{r}\left[ \frac{1}{2}-\frac{1}{6} \right]\]                      \[=\frac{GMm}{3r}\] % increase in energy\[=\frac{\Delta E}{{{U}_{1}}}\times 100\]                 \[=\frac{GMm/3r}{GMm/2r}\times 100=66.7%\]


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