JEE Main & Advanced Sample Paper JEE Main Sample Paper-17

  • question_answer
    A disc of mass M and radius R is performing pure rolling motion in \[X-Y\]plane as shown in figure. The magnitude of angular momentum of the disc about O is

    A)  \[\frac{M{{R}^{2}}\omega }{2}\]                             

    B) \[M{{R}^{2}}\omega \]

    C)  \[\frac{3}{2}\,M{{R}^{2}}\omega \]                       

    D)  \[2\,M{{R}^{2}}\omega \]

    Correct Answer: C

    Solution :

    \[{{\vec{L}}_{o}}={{\vec{L}}_{1}}\] [due to rotational motion of body about an axis passing through the centre of mass] \[{{\vec{L}}_{2}}=\][due to translational motion of the centre of mass about O] \[\Rightarrow \]\[{{\vec{L}}_{o}}=\frac{M{{R}^{2}}}{2}\omega +MR(R\omega )=\frac{3}{2}M{{R}^{2}}\omega \] in clockwise direction.


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