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RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    The surface tension of a soap solution is\[2\times {{10}^{-2}}\]N/m. To blow a bubble of radius 2 cm from 1 cm, the work done is

    A)  \[1.5\pi \times {{10}^{-4}}J\]    

    B) \[1.2\pi \times {{10}^{-4}}J\]

    C)  \[0.3\pi \times {{10}^{-4}}J\]

    D)  \[0.6\pi \times {{10}^{-4}}J\]

    Correct Answer: B

    Solution :

     \[W=2T\Delta A\] \[=2T\times 4\pi (r_{1}^{2}-r_{2}^{2})\] \[=2\times 0.05\times 4\pi \times (4\times {{10}^{4}}-1\times {{10}^{4}})\] \[W=1.2\pi \times {{10}^{-4}}J\]


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