AMU Medical AMU Solved Paper-2004

  • question_answer
    A wire of length L and cross-sectional area A is made of a material of Youngs modulus Y. If the wire is stretched by the amount x. The work done is

    A)  \[\frac{YA{{x}^{2}}}{2L}\]                           

    B)  \[\frac{YA{{x}^{2}}}{L}\]

    C)  \[YA{{x}^{2}}L\]                              

    D)  \[\frac{YAx}{2L}\]

    Correct Answer: A

    Solution :

                     When a wire is stretched, work is done against interatomic forces which is stored as potential energy in the wire, given by \[U=\frac{1}{2}\times \] force extension \[=\frac{1}{2}F\,x\]      ... (i) Also,      \[Y=\frac{stress~}{strain~~}=\frac{F/A}{x/L}\]                   ? (ii) From Eqs. (i) and (ii), we get                 \[U=\frac{1}{2}\frac{YA\,\,x}{L}\,x=\frac{1}{2}\frac{YA\,{{x}^{2}}}{L}\]


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