MGIMS WARDHA MGIMS WARDHA Solved Paper-2012

  • question_answer
    When a force F is applied on a wire of length L and radius r, extension produce is\[l\]. If same force F is applied on the same material wire of length 2 L and radius 2r, then extension will be

    A)  \[l\]                                      

    B)  \[2l\]

    C)  \[l/2\]                                 

    D)  \[4l\]

    Correct Answer: C

    Solution :

                    Youngs elastic coefficient \[Y=\frac{Fl}{\pi {{r}^{2}}\Delta l}\] Wires are of same material, so their Youngs coefficient will be same. \[\therefore \]  \[\frac{{{F}_{1}}{{l}_{1}}}{\pi r_{1}^{2}\Delta {{l}_{1}}}=\frac{{{F}_{2}}{{l}_{2}}}{\pi r_{2}^{2}\Delta {{l}_{2}}}\]                 \[\frac{F\times L}{\pi {{r}^{2}}\times l}=\frac{F\times 2L}{\pi {{(2r)}^{2}}\times \Delta {{l}_{2}}}\]                 \[\Delta {{l}_{2}}=\frac{l}{2}\] Extension produced in the 2nd wire \[=\frac{l}{2}\]


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