I do not believe it's a subject that is considered "hard" but rather your study technique for that subject and how you approach your weaknesses
If you break down the physics syllabus (and the exams) you can divide it into the following: Scientific skill, understanding concepts, rote memorising, mathematical calculations and short/extended answer response technique
I assure you that if you are strong in all these areas, you'd know the syllabus back to front but this would take a considerable amount of time
1. Scientific skills (and prac skills) comes down to how well you know the ideaology behind experiments in the HSC physics curriculum and how you interpret that data
2. Understanding concepts is knowing concepts in a manner that you can explain it effectively explain it to someone else without the need to rote learn. Also look at some "scientific article questions" where they have a random article which makes you explain the theory behind the article. Also do endless past papers to ensure you understand things back to front
3. Rote memorising comes in with history of science as well as societal impacts. You will need to use the "worksheet method" to memorise a large amount of content (please tell me if u need further explanation)
4. Mathematical calculations is best approached with practice. If u don't know what formula to use, look for a random formula within your formula sheet and use that. Some maths questions may assess more than one thing in physics
5. Short answer/extended response is best approached by "predicting the criteria". This is best done by doing endless past papers and understanding the criteria to responses of certain questions
Hope that helps
Best of luck