Hsc was more of a memory game than anything tbh. Especially in the sciences (can't say for physics) where the markers want you to write responses in a certain way and the questions tested you more on random slices of facts/info than actual science sometimes... I roted my essays for english then vomited it back out on paper during exams, I still did somewhat decent. I felt like you could do decently well in Maths if you roted, this probably doesn't apply for 4U though.
tldr: sit down and memorise