JEE Main & Advanced Physics Fluid Mechanics, Surface Tension & Viscosity / द्रव यांत्रिकी, भूतल तनाव और चिपचिपापन Question Bank Self Evaluation Test - Mechanical Properties of Fluids

  • question_answer
    A uniform wooden stick of length L, cross- section area A and density d is immersed in a liquid of density 4rf. A small body of mass m and negligible volume is attached at the lower end of the rod so that the stick floats vertically in stable equilibrium then      

    A) \[m>dAL\]

    B) \[m<dAL\]

    C) \[m<dAL/2\]

    D) \[m<dAL/4\]

    Correct Answer: A

    Solution :

    [a] For equilibrium \[4dA\ell g=(dAL+m)g\] and\[\frac{\ell }{2}>{{Y}_{cm}}\] (for rotational equilibrium) \[{{Y}_{cm}}=\frac{m\times 0+dAL(L/2}{m+dAL}=\frac{dA{{L}^{2}}}{2(m+dAL)}\] \[\ell >\frac{A{{L}^{2}}d}{(ALd+m)}\Rightarrow \frac{m+dAL}{4dA}>\frac{A{{L}^{2}}d}{(ALd+m)}\] \[m>ALd\]


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