JEE Main & Advanced Physics Fluid Mechanics, Surface Tension & Viscosity / द्रव यांत्रिकी, भूतल तनाव और चिपचिपापन Question Bank Pascal's Law and Archimedes Principle

  • question_answer
    Two solids A and B  float in water. It is observed that A floats with \[\frac{1}{2}\] of its body immersed in water and B floats with \[\frac{1}{4}\] of its volume above the water level. The ratio of the density of A to that of B is

    A)            4 : 3                                          

    B)            2 : 3

    C)            3 : 4                                          

    D)            1 : 2

    Correct Answer: B

    Solution :

                       Upthrust = weight of body For A, \[\frac{{{V}_{A}}}{2}\times {{\rho }_{W}}\times g={{V}_{A}}\times {{\rho }_{A}}\times g\Rightarrow {{\rho }_{A}}=\frac{{{\rho }_{W}}}{2}\] For B, \[\frac{3}{4}{{V}_{B}}\times {{\rho }_{W}}\times g={{V}_{B}}\times {{\rho }_{B}}\times g\Rightarrow {{\rho }_{B}}=\frac{3}{4}{{\rho }_{W}}\] (Since 1/4 of volume of B is above the water surface) \ \[\frac{{{\rho }_{A}}}{{{\rho }_{B}}}=\frac{{{\rho }_{W}}/2}{3/4\ {{\rho }_{W}}}=\frac{2}{3}\]


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