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WB JEE Medical WB JEE Medical Solved Paper-2009

  • question_answer
    The Poissons ratio of a material is 0.5. If a  force is applied to a wire of this material, there is a decrease in the cross-sectional area by 4%. The percentage increase in the length is

    A)  1%                                        

    B)  2%

    C)  2.5%                                    

    D)  4%

    Correct Answer: D

    Solution :

                     Poissons ratio = 0.5 Since, density is constant therefore change in volume is zero, we have \[V=A\times l=\text{constant}\] \[\Rightarrow \]               \[\log V=\log A+\log \,l\] or            \[\frac{dA}{A}+\frac{dl}{l}=0\] \[\Rightarrow \]               \[\frac{dl}{l}=-\frac{dA}{A}\] \[\therefore \] Percentage increase in length = 4%


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