BCECE Engineering BCECE Engineering Solved Paper-2010

  • question_answer
    A wooden block is floating in a liquid 50% of its volume inside the liquid when the vessel is stationary. Percentage of volume immersed when the vessel moves upwards with an acceleration\[a=g/3\] is

    A)  30%                                      

    B)  50%

    C)  60%                      

    D)         67%

    Correct Answer: B

    Solution :

    Let densities of wood and liquid are \[{{\rho }_{w}}\]and \[{{\rho }_{l}}\]respectively. When vessel is stationary weight = upthrust ie,           \[V{{\rho }_{w}}g={{V}_{l}}{{\rho }_{l}}g\]                            or            \[\frac{{{V}_{l}}}{V}=\frac{{{\rho }_{w}}}{{{\rho }_{l}}}\]                                ?(i) When the vessel moves upwards with acceleration g/3. upthrust - weight = mass \[\times \] acceleration \[{{V}_{l}}{{\rho }_{l}}\left( g+\frac{g}{3} \right)-V{{\rho }_{w}}g=V{{\rho }_{w}}\times \frac{g}{3}\]                 \[\frac{{{V}_{1}}}{V}=\frac{{{\rho }_{w}}}{{{\rho }_{l}}}\]                              ?(ii) From Eqs. (i) and (ii), we note that \[\frac{{{V}_{l}}}{V}=\frac{{{V}_{l}}}{V}\] ie, fraction of volume immersed in liquid remains unchanged.


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