JIPMER Jipmer Medical Solved Paper-2001

  • question_answer
    A circular disc of mass M and radius r is rotating on a horizontal frictionless table about a diameter, with a constant angular velocity\[\omega .\]If\[m{{r}^{2}}{{\omega }^{2}}\]is \[\Upsilon \] then the kinetic energy of rotation is :

    A)  0.125\[\Upsilon \]                                          

    B)  0.25\[\Upsilon \]                            

    C)  0.5\[\Upsilon \]              

    D)         0.75\[\Upsilon \]

    Correct Answer: A

    Solution :

    Moment of inertia of circular disc is \[I=\frac{m{{r}^{2}}}{2}\]about the centre of mass axis and by perpendicular axis theorem is \[\frac{m{{R}^{2}}}{4}\] about diameter. \[\therefore \] \[K.E.=\frac{1}{2}I{{\omega }^{2}}=\frac{1}{2}\times \frac{1}{4}m{{R}^{2}}\times {{\omega }^{2}}\] \[=\frac{1}{8}m{{R}^{2}}{{\omega }^{2}}\](as\[m{{R}^{2}}{{\omega }^{2}}=Y\]) \[=\frac{1}{8}Y\]


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