NEET Sample Paper NEET Sample Test Paper-42

  • question_answer
    A square gate of size 1m x 1m is hinged at its mid point. A fluid of density p fills space to the left to the gate. The force F required to hold the gate stationary:

    A) \[\frac{\rho \operatorname{g}}{3}\]                    

    B) \[\frac{\rho \operatorname{g}}{2}\]

    C) \[\frac{\rho \operatorname{g}}{6}\]                                

    D) None

    Correct Answer: C

    Solution :

    Net torque above hinge is zero  \[\int\limits_{\operatorname{o}}^{1/2}{\rho \operatorname{g}}\left[ \operatorname{x}+\frac{1}{2} \right].\operatorname{xdx}-\int\limits_{{}}^{1/2}{\rho \operatorname{g}}\left[ \frac{1}{2}-\operatorname{x} \right]\operatorname{xdx}=F.\frac{1}{2}\] \[\rho \operatorname{g}{{\left[ \frac{{{\operatorname{x}}^{3}}}{3}+\frac{1}{2}\frac{{{\operatorname{x}}^{2}}}{2} \right]}_{o}}^{1/2}-\rho \operatorname{g}{{\left[ \frac{{{\operatorname{x}}^{2}}}{2}-\frac{{{\operatorname{x}}^{3}}}{3} \right]}_{o}}^{1/2}=\frac{F}{2}\] On solving we get \[\operatorname{F}=\frac{\rho g}{6}\]


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