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

  • question_answer
    A large open tank has two holes in the wall. One is a square hole of side L at a depth y from the top and the other is a circular hole of radius R at a depth 4y from the top. When the tank is completely filled with water the quantities of water flowing out per second from both the holes are the same. Then R is equal to                         [IIT-JEE (Screening) 2000]

    A)             \[2\pi \,L\]                             

    B)             \[\frac{L}{\sqrt{2\pi }}\]

    C)             L     

    D)             \[\frac{L}{2\pi }\]

    Correct Answer: B

    Solution :

                       Velocity of efflux when the hole is at depth h, \[v=\sqrt{2gh}\] Rate of flow of water from square hole \[{{Q}_{1}}={{a}_{1}}{{v}_{1}}\]= \[{{L}^{2}}\sqrt{2gy}\] Rate of flow of water from circular hole \[{{Q}_{2}}={{a}_{2}}{{v}_{2}}\]= \[\pi {{R}^{2}}\sqrt{2g(4y)}\] According to problem \[{{Q}_{1}}={{Q}_{2}}\] Þ  \[{{L}^{2}}\sqrt{2gy}=\pi {{R}^{2}}\sqrt{2g(4y)}\] \[\Rightarrow \]\[R=\frac{L}{\sqrt{2\pi }}\]


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