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BCECE Engineering BCECE Engineering Solved Paper-2012

  • question_answer
    A soap film of surface tension \[3\times {{10}^{-2}}N{{m}^{-1}}\] formed in a rectangular frame, can support a straw. If the length of the film is 10 cm, then the mass of the straw that film can support is

    A)  0.06 g                  

    B)         0.6 g

    C)  6 g                        

    D)         60 g

    Correct Answer: B

    Solution :

    The weight of straw will be balanced by the force of surface tension. Let the mass of straw is m, then \[mg=2Tl\]                 or            \[m=\frac{2Tl}{g}\]                                 \[=\frac{2\times 3\times {{10}^{-2}}\times 10\times {{10}^{-2}}}{9.8}kg\]                                 \[=0.6\,g\]


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