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BCECE Engineering BCECE Engineering Solved Paper-2011

  • question_answer
    A particle of mass m attached with a string of length l is just revolving on the vertical circle without slacking of the string. If \[{{v}_{A,}}{{v}_{B}}\]  and\[{{v}_{D}}\] are speeds at positions A, B and D, then

    A)  \[{{v}_{B}}>{{v}_{D}}>{{v}_{V}}\]

    B)  tension in string at D = 3 mg

    C)  \[{{v}_{D}}=\sqrt{3gl}\]

    D)  All of the above

    Correct Answer: D

    Solution :

    At A ,                     \[{{v}_{A}}=\sqrt{gl}\] At B,                      \[{{v}_{B}}=\sqrt{5gl}\] and at D,              \[{{v}_{D}}=\sqrt{3gl}\] Thus,     \[{{v}_{B}}>{{v}_{D}}>{{v}_{A}}\] Also,      \[T=3mg(1+cos\theta )\] So, at D, \[\theta ={{90}^{o}}\] \[\therefore \]  \[T=3mg(1+0)=3mg\]


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