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

  • question_answer
    A manometer connected to a closed tap reads 3.5 × 105 N/m2. When the valve is opened, the reading of manometer falls to 3.0 × 105 N/m2, then velocity of flow of water is

    A)            100 m/s                                  

    B)            10 m/s                                    

    C)            1 m/s                                       

    D)             \[10\sqrt{10}\] m/s

    Correct Answer: B

    Solution :

                       Bernoulli's theorem for unit mass of liquid                    \[\frac{P}{\rho }+\frac{1}{2}{{v}^{2}}=\] constant As the liquid starts flowing, it pressure energy decreases  \[\frac{1}{2}{{v}^{2}}=\frac{{{P}_{1}}-{{P}_{2}}}{\rho }\]\[\Rightarrow \frac{1}{2}{{v}^{2}}=\frac{3.5\times {{10}^{5}}-3\times {{10}^{5}}}{{{10}^{3}}}\Rightarrow {{v}^{2}}\] \[=\frac{2\times 0.5\times {{10}^{5}}}{{{10}^{3}}}\Rightarrow {{v}^{2}}=100\Rightarrow v=10\ m/s\]


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