1. The problem statement, all variables and given/known data 2. Relevant equations See above photo. 3. The attempt at a solution Hey guys, I'm stuck on this equation never done anything like it but apparently its due to come up on exam next week. Any ideas on where to go with it so far......i stopped as i was about to remove the integral for U1 as it is constant. As concerns the second part, i'm I right in presuming i work out the thickness, fill that into the given u equation and then in turn use the derived equation to solve Hope ye can help, thanks.