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JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2013

  • question_answer
    Circular disc of mass 2 kg and radius 1 m is rotating about an axis perpendicular to its plane and passing through its centre of mass with a rotational kinetic energy of 8 J. The angular momentum in (j s) is

    A)  8                            

    B)  4

    C)  2                            

    D)  1

    Correct Answer: B

    Solution :

                    \[\frac{1}{2}I{{\omega }^{2}}=8J\] \[\frac{1}{2}\times \frac{1}{2}m{{r}^{2}}{{\omega }^{2}}=8\] \[\frac{1}{4}\times 2\times {{(1)}^{2}}\times {{\omega }^{2}}=8\] \[{{\omega }^{2}}=16\] \[\omega =4rad/s\] \[L=I\omega \] \[=\frac{1}{2}m{{r}^{2}}\omega \] \[=\frac{1}{2}(2)\times {{(1)}^{2}}\times r\] \[=4\,Js\]            


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