I basically have Heat/Thermodynamics and Atomic Nuclear Physics left to do, which ones should I study first? I've looked at both but they both seem so hard for me to understand. I get Heat and some of PV=nRT but I don't get the Root-mean-square speed and how it's derived. I like knowing how to come up with equations because it makes me understand the variables and relationships better. Should I just start memorizing the equations instead of trying to derive them? Also, I'm confused about photons, and I don't really get the definitions given by the book. Which one should I try to takle first and do you have any advice on how to understand it faster? Any sites help at all? Thanks.