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

  • question_answer
    The density \[\rho \] of water of bulk modulus B at a depth y in the ocean is related to the density at surface \[{{\rho }_{0}}\] by the relation

    A) \[\rho ={{\rho }_{0}}\left[ 1-\frac{{{\rho }_{0}}gy}{B} \right]\]        

    B) \[\rho ={{\rho }_{0}}\left[ 1+\frac{{{\rho }_{0}}gy}{B} \right]\]

    C) \[\rho ={{\rho }_{0}}\left[ 1+\frac{Beta }{{{\rho }_{0}}hgy} \right]\]           

    D) \[\rho ={{\rho }_{0}}\left[ 1-\frac{B}{{{\rho }_{0}}gy} \right]\]

    Correct Answer: B

    Solution :

    Bulk modulus, \[B=-{{V}_{0}}\frac{\Delta p}{\Delta V}\Rightarrow \Delta V=-{{V}_{0}}\frac{\Delta p}{B}\]                    Þ \[V={{V}_{0}}\left[ 1-\frac{\Delta p}{B} \right]\]                    \ Density, \[\rho ={{\rho }_{0}}{{\left[ 1-\frac{\Delta p}{B} \right]}^{-1}}={{\rho }_{0}}\left[ 1+\frac{\Delta p}{B} \right]\]                    where, \[\Delta p=p-{{p}_{0}}=h{{\rho }_{0}}g\]                    = pressure difference between depth and surface of ocean            \ \[\rho ={{\rho }_{0}}\left[ 1+\frac{{{\rho }_{0}}gy}{B} \right]\]   (As h = y)


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