# Problem inspired from thermodynamics

1. Nov 29, 2012

### Bipolarity

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

While studying thermodynamics, I constructed the following problem, which I can't seem to solve.

Suppose that $Q_{4} > Q_{3}$ and $|Q_{3}| > |Q_{4}|$. Then for what values of ΔU is it necessarily the case that $|ΔU-Q_{4}| > |ΔU-Q_{3}|$

2. Relevant equations

3. The attempt at a solution
I really have no idea what to do; I solved a much simpler textbook style problem and then decided to consider a more general version of the problem, which led me to this. Any ideas? I conjecture that both the Q values are negative, but is this true? How would I prove it?

BiP

2. Nov 30, 2012

### haruspex

Certainly Q3 < 0, but Q4 need only be smaller in magnitude. You could draw up a truth table to see this, and similarly to deduce the range of ΔU.