JEE Main & Advanced Sample Paper JEE Main - Mock Test - 13

  • question_answer
    The density of water at the surface of ocean is p. If the bulk modulus of water is B, what is the density of ocean water at a depth where the pressure is \[n{{P}_{0}},\] where \[{{P}_{0}}\] is the atmospheric pressure?

    A) \[\frac{\rho B}{B-\left( n-1 \right){{P}_{0}}}\]     

    B)        \[\frac{\rho B}{B+\left( n-1 \right){{P}_{0}}}\]

    C) \[\frac{\rho B}{B-n{{P}_{0}}}\]            

    D) \[\frac{\rho B}{B+n{{P}_{0}}}\]

    Correct Answer: A

    Solution :

    Bulk modulus, \[B=-\frac{\Delta P}{\left( \frac{\Delta V}{{{V}_{0}}} \right)}\,\,\Rightarrow \,\,\Delta V=-{{V}_{0}}\frac{\Delta P}{B}\]
    or \[V-{{V}_{0}}=-{{V}_{0}}\frac{\Delta P}{B}\] (Here \[{{V}_{0}}\]= volume at the surface and V = volume at the depth)
    or \[V={{V}_{0}}-{{V}_{0}}\frac{\Delta P}{B}\,\,\,\,\Rightarrow \,\,\,\,\,V={{V}_{0}}\left( 1-\frac{\Delta P}{B} \right)\]
    \[\therefore \]  Density,  \[\rho '=\frac{m}{V}=\frac{m}{{{V}_{0}}\left( 1-\frac{\Delta P}{B} \right)}\]
    \[=\frac{m}{\frac{m}{\rho }\left( 1-\frac{n{{P}_{0}}-{{P}_{0}}}{B} \right)}\]  \[(\because \,\,\,\Delta P=n{{P}_{0}}-{{P}_{0}})\]
    \[\rho '=\frac{\rho B}{B-(n-1){{P}_{0}}}\]


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