JIPMER Jipmer Medical Solved Paper-2001

  • question_answer
    Ratio of kinetic energy and rotational energy in the motion of a disc is:

    A)  2 : 7      

    B)                                         3 : 1                      

    C)         1 : 2                      

    D)         1 : 1

    Correct Answer: B

    Solution :

    \[{{E}_{k}}=\frac{1}{2}m{{\upsilon }^{2}}+\frac{1}{2}I{{\omega }^{2}}\]                  ?(i) \[\therefore \] Rotational energy \[{{E}_{Rotational\,}}=\frac{1}{2}I{{\omega }^{2}}\]                         ?(ii) Also we know that \[I=m{{K}^{2}}\] so           \[{{K}^{2}}=\frac{{{R}^{2}}}{2}\] and  \[v=R\omega \] Putting the value of \[I\] in equation (i) and (ii), we get \[\frac{{{E}_{k}}}{{{E}_{rotational}}}=\frac{\frac{1}{2}m{{\upsilon }^{2}}+\frac{1}{2}\frac{m{{R}^{2}}}{2}\times \frac{{{\upsilon }^{2}}}{{{R}^{2}}}}{\frac{1}{2}\times \frac{m{{R}^{2}}}{2}\times \frac{{{\upsilon }^{2}}}{{{R}^{2}}}}\] \[=\frac{\frac{3}{4}m{{\upsilon }^{2}}}{\frac{1}{4}m{{\upsilon }^{2}}}=\frac{3}{1}\] hence ratio 3 : 1.


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