NEET Sample Paper NEET Sample Test Paper-56

  • question_answer
    A tank full of water has a small hole in its bottom. If one-fourth of the tank is emptied in \[{{t}_{1}}\]seconds and the remaining three fourths of the tank is emptied in \[{{t}_{2}}\] seconds, then ratio \[\frac{{{t}_{1}}}{{{t}_{2}}}\]is:

    A) \[\sqrt{3}\]                    

    B) \[\sqrt{2}\]        

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

    D) \[\frac{2-\sqrt{3}}{\sqrt{3}}\]

    Correct Answer: D

    Solution :

    [d] Let A and a be cross sectional areas of the tank and hole respectively. Let h be height of water in the tank at a time t. \[Let\,\left[ -\frac{dh}{dt} \right]\] represent the rate of fall of level. \[-\frac{Adh}{dt}=a\sqrt{2gh}\] \[dt=\frac{-A}{a\sqrt{2g}}\frac{dh}{\sqrt{h}}\] Ratio \[\frac{{{t}_{1}}}{{{t}_{2}}}=\frac{\int\limits_{0}^{3{}^{h}/{}_{4}}{\frac{dh}{\sqrt{h}}}}{\int\limits_{3{}^{h}/{}_{4}}^{0}{\frac{dh}{\sqrt{h}}}}=\frac{\sqrt{\frac{3h}{4}}-\sqrt{h}}{0-\sqrt{\frac{3h}{4}}}=\frac{2-\sqrt{3}}{\sqrt{3}}\]


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