JEE Main & Advanced JEE Main Paper Phase-I (Held on 09-1-2020 Evening)

  • question_answer
    A small spherical droplet of density d is floating exactly half immersed in a liquid of density \[\rho \]and surface tension T. The radius of the droplet is (take note that the surface tension applies an upward force on the droplet) [JEE MAIN Held on 09-01-2020 Evening]

    A) \[r=\sqrt{\frac{3T}{(2d-\rho )g}}\]

    B) \[r=\sqrt{\frac{T}{(d+\rho )g}}\]

    C) \[r=\sqrt{\frac{T}{(d-\rho )g}}\]

    D) \[r=\sqrt{\frac{2T}{3(d+\rho )g}}\]

    Correct Answer: A

    Solution :

    \[T.2\,\,\pi r+\frac{2}{3}\pi {{r}^{3|}}\rho g=\frac{4}{3}\pi {{r}^{3}}dg\] \[T=\frac{{{r}^{2}}}{3}\,(2d-\rho )g\] \[r=\sqrt{\frac{3T}{(2d-\rho )g}}\]


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