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JEE Main & Advanced Physics NLM, Friction, Circular Motion Question Bank Self Evaluation Test - Laws of Motion

  • question_answer
    A particle tied to a string describes a vertical circular motion of radius r continually. If it has a velocity \[\sqrt{3gr}\] at the highest point, then the ratio of the respective tensions in the string holding it at the highest and lowest points is

    A) \[4:3\]

    B) \[5:4\]  

    C) \[1:4\]

    D) \[3:2\]

    Correct Answer: C

    Solution :

    [c] Tension at the highest point \[{{T}_{top}}=\frac{m{{v}^{2}}}{r}-mg=2mg\left( \therefore {{v}_{top}}=\sqrt{3gr} \right)\] Tension at the lowest point \[{{T}_{bottom}}=2mg+6mg=8mg\] \[\therefore \frac{{{T}_{top}}}{{{T}_{bottom}}}=\frac{2mg}{8mg}=\frac{1}{4}.\]


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