# Homework Help: Area of Thermal Expansion

1. Sep 27, 2012

### vkt420

1. The problem statement, all variables and given/known data
A non-isotropic material is heated, fractional increase in length is different along different directions. With length l1=6.1 cm and l2=6.0 cm. In direction of l1, the coefficient expansion is $\alpha$1= 10×10-5 K-1 and direction l2 is $\alpha$2= 40×10-5K-1. The plate is heated until it becomes a perfect square. What is the area of the square? (The answer is 38 cm2) I just don't know how use the equations with out a given temperature.

2. Relevant equations
ΔL=$\alpha$L0T
Lx=Lx0+Lx0$\alpha$ΔT
Ly=Ly0+Ly0$\alpha$ΔT
A0=Lx0Ly0
A=LxLy

3. The attempt at a solution
Not sure what to do with the equations without the temperature.

2. Sep 27, 2012

### voko

You need to find the temperature from the condition that the rectangular becomes square.