I noted in a previous response by MEDGIRL that most of the physics formulas were provided on the actual MCAT whereas Kaplan practice items require them from memory.
I second Alshephard....LEARN the formulas! I found that many of the familar formulas that I "knew" by heart ended up rearranged into wierd configurations when they DID give them to you on the test. It was much easier for me to use the formulas I knew how to work than to try to figure out how they had rearranged them (and THEN figure out the answer). The key here is TIME! If you are a math wiz (I'm not)and deriving equations is easy for you, then knowing the basic formulas will be enough. If your more like me, start memorizing EVERYTHING!