J & K CET Engineering J and K - CET Engineering Solved Paper-2006

  • question_answer
    Water flows steadily through a horizontal pipe of variable cross-section. If the pressure of water is p at a point where flow speed is v, the pressure at another point where the flow of speed is \[2\text{ }v,\]is (take density of water as p)

    A)  \[p-\frac{3\,\rho {{v}^{2}}}{2}\]

    B)  \[p-\frac{\,\rho {{v}^{2}}}{2}\]

    C)  \[p-\frac{3\,\rho {{v}^{2}}}{4}\]

    D)  \[p-\rho {{v}^{2}}\]

    Correct Answer: A

    Solution :

    From Bernoulli's equation, the sum of all forms of energy in a fluid flowing along an enclosed path (a streamline) is the same at any two points in the path. Therefore, \[p+\frac{1}{2}\rho v_{1}^{2}=p'+\frac{1}{2}\rho v_{2}^{2}\] Given, \[{{v}_{2}}=2v,\,\,\,\,\,\,\,{{v}_{1}}=v\] \[\therefore \] \[p+\frac{1}{2}\rho {{v}^{2}}=p'+\frac{1}{2}\rho {{(2v)}^{2}}\] \[\Rightarrow \] \[p'=p-\frac{3}{2}\rho {{v}^{2}}\].


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