J & K CET Medical J & K - CET Medical Solved Paper-2012

  • question_answer
    A coin of mass 10 g rolls along a horizontal table with a velocity of 6 cm/s. Its total kinetic energy is

    A)  \[9\,\mu J\]             

    B)  \[18\,\mu J\]

    C)  \[27\,\mu J\]            

    D)  \[36\,\mu J\]

    Correct Answer: C

    Solution :

     The total kinetic energy of the coin is \[K={{K}_{\tau }}+{{K}_{R}}\] \[=\frac{1}{2}m{{v}^{2}}+\frac{1}{2}I{{\omega }^{2}}\] For coin, the moment of inertia \[I=\frac{1}{2}M{{R}^{2}}\] \[\therefore \] \[K=\frac{1}{2}m{{v}^{2}}+\frac{1}{4}M{{v}^{2}}\] \[(\because v=r\omega )\] \[=\frac{3}{4}M{{v}^{2}}\] \[=\frac{3}{4}\times (10\times {{10}^{-3}}){{(6\times {{10}^{-2}})}^{2}}\] \[=27\times {{10}^{-6}}J=27\mu J\]


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