# Calculate variation in volume using given Poisson's ratio

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1. Nov 22, 2015

### abhishek4

1. The problem statement, all variables and given/known data: A cylinder is elongated by 2% of its original length. If Poisson's ratio of its material is 0.3. Calculate the percentage variation in volume.

2. Relevant equations
V = πr^2l
η= 0.3= Δl/l/Δr/r

3. The attempt at a solution
I tried using calculus to differentiate V to find change in volume and then divided it by the given volume but could not find and answer as r^2 was left.

2. Nov 22, 2015

### haruspex

I think you have the definition of Poisson's ratio wrong. It should be the other way up and negated: $-\frac{\Delta r/r}{\Delta l/l}$.