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

  • question_answer
    The gravitational field, due to the 'left over part* of a uniform sphere (from which a part as shown, has been 'removed out'), at a very far off point, P, located as shown, would be (nearly):

    A) \[\frac{5}{6}\frac{GM}{{{x}^{2}}}\]

    B) \[\frac{8}{9}\frac{GM}{{{x}^{2}}}\]

    C) \[\frac{7}{8}\frac{GM}{{{x}^{2}}}\]

    D) \[\frac{6}{7}\frac{GM}{{{x}^{2}}}\]

    Correct Answer: C

    Solution :

    [c] Let mass of smaller sphere (which has to be removed) is m Radius \[=\frac{R}{2}\] (from figure) \[\frac{M}{\frac{4}{3}\pi {{R}^{3}}}=\frac{m}{\frac{4}{3}\pi {{\left( \frac{R}{2} \right)}^{3}}}\Rightarrow m=\frac{M}{8}\] Mass of the left over part of the sphere \[M'=M-\frac{M}{8}=\frac{7}{8}M\] Therefore gravitational field due to the left over part of the sphere \[=\frac{GM'}{{{x}^{2}}}=\frac{7}{8}\frac{GM}{{{x}^{2}}}\]


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