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

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    A large tank filled with water to a height ?h? is to be emptied through a small hole at the bottom. The ratio of time taken for the level of water to fall from h to \[\frac{h}{2}\] and from \[\frac{h}{2}\] to zero is                                         [EAMCET (Engg.) 2003]

    A)            \[\sqrt{2}\]                           

    B)            \[\frac{1}{\sqrt{2}}\]        

    C)            \[\sqrt{2}-1\]                       

    D)            \[\frac{1}{\sqrt{2}-1}\]

    Correct Answer: C

    Solution :

                       Time taken for the level to fall from H to \[H'\]     \[t=\frac{A}{{{A}_{0}}}\sqrt{\frac{2}{g}}\,\,\left[ \sqrt{H}-\sqrt{H'} \right]\] According to problem- the time taken for the level to fall from h to \[\frac{h}{2}\]     \[{{t}_{1}}=\frac{A}{{{A}_{0}}}\sqrt{\frac{2}{g}}\ \ \left[ \sqrt{h}-\sqrt{\frac{h}{2}} \right]\] and similarly time taken for the level to fall from \[\frac{h}{2}\] to zero    \[{{t}_{2}}=\frac{A}{{{A}_{0}}}\sqrt{\frac{2}{g}}\ \left[ \sqrt{\frac{h}{2}}-0 \right]\] \[\therefore \ \frac{{{t}_{1}}}{{{t}_{2}}}=\frac{1-\frac{1}{\sqrt{2}}}{\frac{1}{\sqrt{2}}-0}=\sqrt{2}-1.\]


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