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Question: Answered & Verified by Expert
The poisson's 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 :
PhysicsMechanical Properties of SolidsWBJEEWBJEE 2009
Options:
  • A $1 \%$
  • B $2 \%$
  • C $2.5 \%$
  • D $4 \%$
Solution:
2297 Upvotes Verified Answer
The correct answer is: $4 \%$
Poisson ratio $=0.5$
Therefore density is constant hence change in volume is zero we have $\mathrm{V}=\mathrm{A} \times \ell=$ constant
$\log \mathrm{V}=\log \mathrm{A}+\log \ell$ or $\frac{d A}{A}+\frac{d \ell}{\ell}=0 \Rightarrow \frac{d \ell}{\ell}=-\frac{d A}{A}$
That is $4 \%$

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