AFMC AFMC Solved Paper-2008

  • question_answer
    A rectangular vessel when full of water, takes 10 min to be emptied through an orifice in its bottom- How much time will it take to be emptied when half filled with water?

    A) 9 min                                    

    B) 7 min

    C) 5 min                                    

    D) 3 min

    Correct Answer: B

    Solution :

    If \[{{A}_{0}}\]is the area of orifice at the bottom below the free surface and A that of vessel, time t taken to be empited the tank, \[t=\frac{A}{{{A}_{0}}}\sqrt{\frac{2H}{g}}\] \[\therefore \]     \[\frac{{{t}_{1}}}{{{t}_{2}}}=\sqrt{\frac{{{H}_{1}}}{{{H}_{2}}}}\] \[\Rightarrow \]    \[\frac{t}{{{t}_{2}}}=\sqrt{\frac{{{H}_{2}}}{{{H}_{1}}/2}}\] \[\Rightarrow \]   \[\frac{t}{{{t}_{2}}}=\sqrt{2}\] \[\therefore \]  \[{{t}_{2}}=\frac{t}{\sqrt{2}}=\frac{10}{\sqrt{2}}=5\sqrt{2}\]\[\approx 7\,\min \]


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