Railways Technical Ability Fluid Mechanics and Machinery Question Bank Fluid Mechanics

  • question_answer             Which one of the following represents equilibrium of a static fluid? (Symbols have the usual meaning)

    A) \[\frac{dp}{dz}=-\frac{\rho }{g}\]                      

    B) \[\frac{dp}{g}\,=\,-\,\frac{dz}{\rho }\]

    C) \[\rho \,dp=-\frac{dz}{g}\]                      

    D) \[\frac{dp}{\rho }=-g\,dz\]

    Correct Answer: D

    Solution :

    Bernoulli's equation is: \[\frac{{{v}^{2}}}{2g}+\frac{p}{\rho g}+z=const\] \[For\,\,v=0,\]\[\frac{p}{\rho g}+z=const\] \[\frac{p}{\rho g}+z=const\] \[dp/\rho +gdz=0\] or \[\frac{dp}{\rho }=-gdz\]

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