RAJASTHAN PMT Rajasthan - PMT Solved Paper-2004

  • question_answer
    The radius of gyration of a hollow spherical shell is 2.5 J. If its frequency of rotation is made 10 times, then new kinetic energy will be:

    A)  250 J                                    

    B)  0.25 J

    C)  2500 J                  

    D)         2.5 J

    Correct Answer: A

    Solution :

    Given: \[{{K}_{rot}}\]= 2.5 J, \[{{\omega }_{1}}\]= \[\omega ,\]\[{{\omega }_{2}}\] = 10 \[\omega \] Rotational kinetic energy \[{{K}_{rot}}=\frac{1}{2}I{{\omega }^{2}}\]             or                \[{{K}_{rot}}\propto {{\omega }^{2}}\]                 \[\therefore \]  \[\frac{K{{}_{rot}}}{K{{}_{rot}}}={{\left( \frac{{{\omega }_{2}}}{{{\omega }_{1}}} \right)}^{2}}={{(10)}^{2}}=100\] \[\therefore \]  \[K{{}_{rot}}=100\times 2.5=250\,\text{J}\]


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