JEE Main & Advanced Physics Gravitation / गुरुत्वाकर्षण Question Bank Self Evaluation Test - Gravitation

  • question_answer
    A satellite of mass m is orbiting the earth in a circular orbit of radius R. It starts losing energy due to small air resistance at the rate of C J/s. Find the time taken for the satellite to reach the earth.

    A) \[\frac{GMm}{C}\left[ \frac{1}{R}-\frac{1}{r} \right]\]

    B) \[\frac{GMm}{2C}\left[ \frac{1}{R}+\frac{1}{r} \right]\]

    C) \[\frac{GMm}{2C}\left[ \frac{1}{R}-\frac{1}{r} \right]\]

    D) \[\frac{2GMm}{C}\left[ \frac{1}{R}+\frac{1}{r} \right]\]

    Correct Answer: C

    Solution :

    [c]  \[E=-\frac{GMm}{2r}\] \[-\frac{dE}{dt}=\frac{GMm}{2r}\frac{1}{{{r}^{2}}}\frac{dr}{dt}\] \[\int\limits_{0}^{t}{dt=-\frac{GMm}{2C}\int\limits_{r}^{R}{\frac{dr}{{{r}^{2}}};t=\frac{GMm}{2C}\left[ \frac{1}{R}-\frac{1}{r} \right]}}\]


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