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

  • question_answer
    Three particles P, Q and R are placed as per given figure. Masses of P, Q and R are \[\sqrt{3}m,\,\,\sqrt{3}m\] and m respectively. The gravitational force on a fourth particle S of mass m is equal to

    A) \[\frac{\sqrt{3}G{{M}^{2}}}{2{{d}^{2}}}\]in ST direction only

    B) \[\frac{\sqrt{3}G{{M}^{2}}}{2{{d}^{2}}}\]in SQ direction and \[\frac{\sqrt{3}G{{M}^{2}}}{2{{d}^{2}}}\]in SU direction

    C) \[\frac{\sqrt{3}G{{M}^{2}}}{2{{d}^{2}}}\]  in SQ direction only

    D)  \[\frac{\sqrt{3}G{{M}^{2}}}{2{{d}^{2}}}\]in SQ direction and \[\frac{\sqrt{3}G{{M}^{2}}}{2{{d}^{2}}}\] in ST direction

    Correct Answer: C

    Solution :

    [c] In horizontal direction \[Net\,force=\frac{G\sqrt{3}mm}{12{{d}^{2}}}\cos {{30}^{\operatorname{o}}}-\frac{G{{m}^{2}}}{4d}\cos {{60}^{\operatorname{o}}}\]\[=\frac{G{{m}^{2}}}{8{{d}^{2}}}-\frac{G{{m}^{2}}}{8{{d}^{2}}}=0\] In vertical direction, Net force \[=\frac{G\sqrt{3}{{m}^{2}}}{12{{d}^{2}}}\cos {{60}^{\operatorname{o}}}+\frac{G\sqrt{3}{{m}^{2}}}{3{{d}^{2}}}+\frac{G{{m}^{2}}}{4d}\cos {{30}^{\operatorname{o}}}\] \[=\frac{\sqrt{3}G{{m}^{2}}}{24{{d}^{2}}}+\frac{\sqrt{3}G{{m}^{2}}}{3{{d}^{2}}}+\frac{\sqrt{3}G{{m}^{2}}}{8d}\] \[=\frac{\sqrt{3}G{{m}^{2}}}{{{d}^{2}}}\left[ \frac{1+8+3}{24} \right]=\frac{\sqrt{3}G{{m}^{2}}}{2{{d}^{2}}}\]along SQ-


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