Hey,
Don't stress too much over the physics section. I was going through the same thing...scoring HORRIBLY on practice exams, yet I ended up knowing more than I thought when I took the OAT. Physics was sadly one of my weaker subjects in undergrad, but I pulled through with a 330...not spectacular, but definitely not horrible either. I agree with everyone else...study the concepts, especially Newton's Laws and know the Kinematics equations like the back of your hand because I rememeber there were at least 2-3 questions on those...along with elastic and inelastic collisions and friction. If you are stuck on a question, mark it and go to the next. Do not waste time staring at one question for too long because you could be using that time to knock down the next 2 or 3 questions for more points. Skip around, get to the end, then go back...if you only have 3-5 minutes left, you might as well do the "bcbcbcbc" thing to whatever is left. It's better than leaving anything blank.
Good Luck! Relax, and you'll be fine.