# Homework Help: Thermal equilibrium of system

1. Apr 26, 2010

### sarahaha288

1. The problem statement, all variables and given/known data

I need to calculate dS/dU for a solid when then system is in thermal equilibrium.
Na=100
Nb=10
U=20e

2. Relevant equations

I rearranged the equation to find that Ds/Du=kb(1/omega)(dOMEGA/dU)

3. The attempt at a solution
I am not sure how to go about this because I am not sure when the system is in thermal equilibrium and how to find (dS/dU) for the equation. any help would be greatly appreciated.

2. Apr 27, 2010

### sarahaha288

Any takers? any advice is appreicated!

3. Apr 27, 2010

### Mapes

Hi sarahaha288, you'll probably get more responses if you add some context to the problem and proofread your post carefully in LaTeX. I've done a lot of entropy calculations, but I have no idea what "Na=100 Nb=10" is referring to, for example. If you give the complete problem statement and write your equations cleanly as

$$\frac{dS}{dU}=k_B\left(\frac{1}{\Omega}\right)\left(\frac{d\Omega}{dU}\right)$$

(click on the equation to see the markup language) then I'm sure you'll get some help very soon.