The maths and physics is nothing to worry about...GCSE level if that. There are millions of threads on this so have a quick search and you should find all you need. Visit the OAA website for an idea of the structure of the assessment.
Best piece of advise i could give you is to relax and try not to be too nervous...i know a few people who scored low on the hand-eye co-ordination tests as they were shaking with nerves.
Good luck
wish2fly