Punjab Medical Punjab - MET Solved Paper-2008

  • question_answer
    A liquid drop of radius \[R\] breaks into 64 tiny drops each of radius\[r\]. If the surface tension of the liquid is \[T\], then the gain in energy is

    A) \[48\pi {{R}^{2}}T\]                        

    B) \[12\pi {{r}^{2}}T\]

    C) \[96\pi {{R}^{2}}T\]                        

    D) \[192\pi {{r}^{2}}T\]

    Correct Answer: D

    Solution :

    Volume of big drop = 64 x volume of tiny drops or            \[\frac{4}{3}\pi {{R}^{3}}=64\times \frac{4}{3}=\pi {{r}^{3}}\] or            \[R=4r\] So, the gain in surface energy = work done in splitting a liquid drop of radius\[R\] into \[n\] identical drops                 \[=4\pi T{{R}^{2}}({{n}^{1/3}}-1)\]                 \[=4\pi T{{(4r)}^{2}}({{64}^{1/3}}-1)=192\pi {{r}^{2}}T\]


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