NEET Physics Elasticity NEET PYQ-Elasticity

  • question_answer
    Copper of fixed volume V is drawn into wire of length \[l\]. When this wire is subjected to a constant force F, the extension produced in the wire is\[\Delta l\]. Which of the following graphs is a straight line? [NEET 2014]

    A) \[\Delta l\] versus \[\frac{1}{l}\]   

    B) \[\Delta l\] versus \[{{l}^{2}}\]

    C) \[\Delta l\] versus \[\frac{1}{{{l}^{2}}}\]

    D) \[\Delta l\] versus \[l\]

    Correct Answer: B

    Solution :

    For Hooke's law. Young Modulus
    \[y=\frac{F/A}{\Delta l/l}=\frac{F\times l}{\Delta l\times A}\]
    \[V=A\times l=\] constant
    From Eqs. (i) and (ii),
    \[y=\frac{F\times l\times l}{\Delta l\times V}\]                  …(i)
    \[\Delta \,l=\frac{F}{V\times y}{{l}^{2}}\]              …(ii)
    \[\Rightarrow \]   \[\Delta l\propto {{l}^{2}}\]


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