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  5. Fluid Mechanics, Surface Tension & Viscosity / द्रव यांत्रिकी, भूतल तनाव और चिपचिपापन

JEE Main & Advanced Physics Fluid Mechanics, Surface Tension & Viscosity / द्रव यांत्रिकी, भूतल तनाव और चिपचिपापन JEE PYQ-Fluid Mechanics, Surface Tension and Viscosity

  • question_answer
    A small soap bubble of radius 4 cm is trapped inside another bubble of radius 6 cm without any contact. Let \[{{P}_{2}}\]be the pressure inside the inner bubble and\[{{P}_{0}},\]the pressure outside the outer bubble. Radius of another bubble with pressure difference \[{{P}_{2}}-{{P}_{0}}\] between its inside and outside would be                                                                                                                                     [JEE Main Online 16-4-2018]

    A)  6 cm               

    B)  12 cm

    C)  4.8 cm

    D)       2.4 cm

    Correct Answer: D

    Solution :

    [d] As we enter a soap bubble the pressure increases by \[\frac{4T}{R}\]
    Here is radius of bubble, and is surface tension.
                \[{{P}_{2}}={{P}_{0}}+\frac{4T}{4}+\frac{4T}{6}\]
    \[{{p}_{2}}={{P}_{0}}+\frac{5}{12}\times 4T\]
    \[{{p}_{2}}-{{P}_{0}}=\frac{4T}{\frac{12}{5}}\]
    So for a single bubble to have a pressure difference of\[{{P}_{2}}-{{P}_{0}}\]
    \[R=\frac{12}{5}=2.4\,cm\]


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