JEE Main & Advanced Physics Gravitation / गुरुत्वाकर्षण Question Bank Gravitation Potential

  • question_answer
    A body of mass m kg. starts falling from a point  2R above the Earth?s surface. Its kinetic energy when it has fallen to a point ?R? above the Earth?s surface [R-Radius of Earth, M-Mass of Earth, G-Gravitational Constant]     [MP PMT 2002]

    A)             \[\frac{1}{2}\frac{GMm}{R}\]

    B)               \[\frac{1}{6}\frac{GMm}{R}\]

    C)             \[\frac{2}{3}\frac{GMm}{R}\]

    D)               \[\frac{1}{3}\frac{GMm}{R}\]

    Correct Answer: B

    Solution :

                    Potential energy \[U=\frac{-GMm}{r}=-\frac{GMm}{R+h}\]             \[{{U}_{initial}}=-\frac{GMm}{3R}\] and \[{{U}_{final}}=-\frac{-GMm}{2R}\] Loss in PE = gain in \[KE=\frac{GMm}{2R}-\frac{GMm}{3R}=\frac{GMm}{6R}\]


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