Yeah, logarithms is probably the only thing (and even then, it's only in the HSC course, not in Prelim., which is what OP asked).I myself did general last year (weird school and weird hsc system) and this year I'm doing chem and the only thing so far I've come across that I didnt learn in general is Logarithms. Outside of that, I dont think there is much more you need to know that general doesnt cover.
That was the case before the current syllabus. In the current HSC Physics syllabus (2001 onwards), no knowledge of 2U maths is assumed or required.I think you can. If you want to do physics you'll need at least 2 unit (according to my physics teacher)