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JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2014

  • question_answer
    A disc having mass M and radius R is rotating with angular velocity \[\frac{4\omega }{5}\], another disc of mass 2M and radius \[\frac{2\omega }{5}\] is placed coaxially on the ' first disc gently. The angular velocity of the system will be

    A) \[\frac{3\omega }{5}\]                                  

    B) \[\frac{2\omega }{3}\]

    C) \[\mu =\frac{3}{2}\]                                      

    D) \[\mu =\frac{4}{3}\]

    Correct Answer: D

    Solution :

                    First, we find out the moment of inertia of the disc about the axis passing the centre and normal to through the plane is \[\mu \] So, for first disc, \[W\] Similarly, for second disc, \[\frac{4W}{3}\] Total moment of inertia of the whole system \[\frac{5W}{2}\]                 \[=\frac{3}{4}M{{R}^{2}}\] According to the conservation of angular momentum \[\sigma =\text{5}.\text{67}\times \text{1}{{0}^{-\text{8}}}\text{W}-{{\text{m}}^{\text{2}}}{{\text{K}}^{\text{-4}}}\] \[y=5\sin \frac{\pi x}{3}\cos 40\pi t\] \[t\]


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