# Poisson's ratio

1. Aug 6, 2005

### saravanan_n

can anybody please tell me how this equation has been arrived?

dA=A(1-m dL/L)^2 -A

where
A=Area of cross section
L=length

2. Aug 6, 2005

### marlon

Whithin what context did you acquire this equation ?

marlon

3. Aug 6, 2005

### EnumaElish

What is m?

Looks to me it's a formula for calculating the % change in cross-sectional area for a % stretch lengthwise. Cross-section area is a function of the width (or perhaps width x length). But width is compressed as length is stretcehd and that has to be taken into account while calculating the change in area.

Having written all this, I don't get why a squared term is involved, because while the calculation of an area may involve a square, the change in such an area would be linear.

From a Yahoo search on "Poisson's ratio":
http://www.millersv.edu/~jdooley/macro/derive/elas1/poissn/poissn.htm