JEE Main & Advanced Sample Paper JEE Main Sample Paper-4

  • question_answer
    Which of the following quantities remain constant in a planetary motion (consider elliptical orbits) as seen from the sun?

    A)  speed                 

    B)  angular speed

    C)  kinetic energy                 

    D)  angular momentum

    Correct Answer: D

    Solution :

    As force acting on planet is central in nature so torque acting on planet is zero about the satellite & hence its angular momentum remains constant. In elliptical orbit as planet revolves around the sun, the seperation between sun & planet changes & hence moment of inertia which in turn changes the angular velocity to keep angular momentum constant. \[K=\frac{{{L}^{2}}}{2I}\]as I changes, K also changes.

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