Hi, I am studying for the MCATs, and currently going through physics. Sadly its my weakest area :( For the last three weeks I am stuck on conservative/non-conservative forces. The problem seems to be that I keep missing important associated forces on a system. For example: I got stuck with problem 62 and 42 here: http://www.astro.queensu.ca/~tjb/hw/P10706/hw6.pdf The problem? for 42- I simply didnt include the F of the engine in the free diagram- and all other forces canceled out. For 62: I assumed that for the skier to be able to continue straight the final KE just has to be greater than the Centripetal force. Skipped over the fact that I can just make mg= mv^2/r and then solve the work energy equation. I had a couple of similar "ahh" moments with other force problems. Soooo- Any tips for specific exercises/problems/ approaches to make sure that I don't miss key aspects of the system?? Thanks