NEET Sample Paper NEET Sample Test Paper-76

  • question_answer
    If the density of water at the surface of the lake is D. The bulk modulus of water is B, then the density of lake water at a depth where the pressure is n p? \[[p :atomospheric pressure]\]

    A)  \[\frac{DB}{B+(n-1)p}\]                       

    B)  \[\frac{DB}{B-(n-1)p}\]

    C)  \[\frac{DB}{B+(n\,+1)p}\]                  

    D)  None of these

    Correct Answer: A

    Solution :

    Pressure at surface of lake = p (atoms pressure) Pressure at the depth = np (given) \[\therefore \,\, increase or cahnge in pressure \left( \Delta p \right) =np - p\] Suppose V is the volume of a certain mass M of water at the surface then \[\operatorname{M} = DV\] Now decrease in volume due to increase in pressure \[\Delta p\] is \[\Delta \,V=\frac{V\Delta p}{B}\] Volume of the mass M of water at given depth is \[V'\,\,=\,\,V-\Delta V=V\,\,-\frac{V\Delta p}{B}\] \[=\,\,\,V\left( 1-\frac{\Delta p}{B} \right)=\frac{V}{B}(B\,\,-\Delta p)\] Density of water at that depth is \[D'=\frac{M}{V'}=\frac{DV}{V'}=\frac{DV}{\frac{V}{B}(B-\Delta p)}=\frac{DB}{B-\Delta p}=\frac{DB}{B-(n-1)p}\]


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