JEE Main & Advanced Physics Fluid Mechanics, Surface Tension & Viscosity / द्रव यांत्रिकी, भूतल तनाव और चिपचिपापन Question Bank Self Evaluation Test - Mechanical Properties of Fluids

  • question_answer
    An air bubble of radius 1 cm rises with terminal velocity 0.21 cm/s in liquid column. If the density of liquid is\[1.47\times {{10}^{3}}kg/{{m}^{3}}\]. Then the value of coefficient of viscosity of liquid ignoring the density of air, will be        

    A) \[1.71\times {{10}^{4}}poise\]

    B) \[1.82\times {{10}^{4}}poise\]

    C) \[1.78\times {{10}^{4}}poise\]

    D) \[1.52\times {{10}^{4}}poise\]

    Correct Answer: D

    Solution :

    [d] Using the formula of the terminal velocity of a body falling through a viscous medium, \[V=\frac{2{{r}^{2}}(\rho -\sigma )g}{9\eta }\Rightarrow \eta =\frac{2{{r}^{2}}(\rho -\sigma )g}{9v}\] Where \[\rho \] is the density of material of body and \[\sigma \]is the density of medium. In case of the air bubble\[\rho =1\] and\[\sigma =1.47\times {{10}^{3}}kg/ms\] the air bubble rises up. \[\eta =\frac{2{{r}^{2}}\sigma g}{9v}=\frac{2\times {{({{10}^{-2}})}^{2}}\times 1.47\times {{10}^{3}}\times 9.8}{9\times 0.21\times {{10}^{-2}}}\] \[=1.52\times {{10}^{3}}\] decapoise \[=1.52\times {{10}^{4}}\] Poise


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