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JEE Main & Advanced Physics Fluid Mechanics, Surface Tension & Viscosity / द्रव यांत्रिकी, भूतल तनाव और चिपचिपापन Question Bank Pressure Difference

  • question_answer
    The pressure of air in a soap bubble of 0.7cm diameter is 8 mm of water above the pressure outside. The surface tension of the soap solution is [MP PET 1991; MP PMT 1997]

    A)             \[100dyne/cm\]

    B)             \[68.66dyne/cm\]

    C)             \[137dyne/cm\]

    D)                      \[150dyne/cm\]

    Correct Answer: B

    Solution :

                    \[\Delta P=\frac{4T}{r}=hdg\Rightarrow T=\frac{rhdg}{4}\] \[=\frac{0.35\times 0.8\times 1\times {{10}^{3}}}{4}\]                  \[=70\ dyne/cm\]\[\equiv 68.66\ dyne/cm\]


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