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
    If 'M' is the mass of water that rises in a capillary tube of radius 'r', then mass of water which will rise in a capillary tube of radius '2r' is :                                                                           [JEE Main 9-4-2019 Morning]

    A) \[4M\]               

    B)      \[M\]

    C) \[2M\]               

    D)      \[\frac{M}{2}\]

    Correct Answer: C

    Solution :

    [c] Height of liquid rise in capillary tube \[h=\frac{2T\cos {{\theta }_{C}}}{\rho rg}\]\[\Rightarrow h\propto \frac{1}{r}\]
    when radius becomes double height become half
    \[\therefore \]\[h'=\frac{h}{2}\]
    Now,\[M=\pi {{r}^{2}}h\times \rho \]and \[M'=\pi {{(2r)}^{2}}(h/2)\times \rho =2M\]
    Option [c]


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