NEET Sample Paper NEET Sample Test Paper-56

  • question_answer
    If the angular momentum of a rotating body about a fixed axis is increased by 10%. Its kinetic energy will be increased by:

    A) 10%                 

    B) 20%    

    C) 21%                 

    D) 5%

    Correct Answer: C

    Solution :

    [c] \[K.E=\frac{{{L}^{2}}}{2M}\] \[{{L}_{1}}={{L}_{0}}{{L}_{2}}={{L}_{0}}+\frac{10{{L}_{0}}}{100}\] \[{{L}_{1}}={{L}_{0}}{{L}_{2}}+\frac{11{{L}_{0}}}{10}\] \[{{K}_{1}}=\frac{L_{0}^{2}}{2M}{{K}_{2}}=\frac{121L_{0}^{2}}{100\times 2M}\] \[\Delta K=\frac{L_{0}^{2}}{2M}\left[ \frac{121}{100}-1 \right]=\frac{21}{100}\frac{L_{0}^{2}}{2M}\] \[\frac{\Delta K}{K}%\frac{\left[ \frac{121}{100}-1 \right]\frac{L_{0}^{2}}{2M}}{\frac{L_{0}^{2}}{2M}}\times 100\] \[=21%\] Note: % change in quantity \[\left( \Delta K=\frac{{{K}_{2}}-{{K}_{1}}}{{{K}_{1}}} \right)\]


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