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JEE Main & Advanced Sample Paper JEE Main Sample Paper-15

  • question_answer
    Two insects P and Q are firmly sitting at the ends of a mass less semicircular wire of radius R and two more insects A and B are firmly sitting at the bottom of the wire. The wire is given an angular velocity\[{{\omega }_{0}}\]about a vertical axis through its centre as shown in the figure. Mass of each insect is M, Now A and B crawl to the opposite ends to meet P and Q. Final angular velocity attained by the rod is equal to

    A) \[\frac{{{\omega }_{0}}}{4}\]                                     

    B) \[\frac{{{\omega }_{0}}}{2}\]

    C) \[{{\omega }_{0}}\]                                        

    D) \[2{{\omega }_{0}}\]

    Correct Answer: B

    Solution :

    \[{{\overrightarrow{L}}_{i}}={{\overrightarrow{L}}_{f}}\] \[(2m{{R}^{2}}){{\omega }_{0}}=(2m{{R}^{2}}+2m{{R}^{2}})w'\]\[w'=\frac{{{\omega }_{0}}}{2}\]


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