Instead of bashing through 100 practice exams and repeating 100 inelastic and momentum conservation questions that are always the same, I think its a good idea all of us to post some questions you found challenging and discuss.
Personally, I find those electronic questions hard (which I have already posted in recent threads) where you got to find where to place Vout in order to obtain a desired output voltage.
Gravitation is rather hard especially the calculator work. Always forgetting the ^3 or ^2 or root because the numbers are so big. Other than that its pretty straight forward application of formulae. Actually, although I have not came into any in VCAA exams, those that involve fractions are actually quite tricky. Such as find the acceleration if the mass of planet is 1/2 of earth and radius is 1/3 of earth or something.
Motion, I mainly do not understand that 2010 neap lawn mower question...like how is that net force etc...kinda weird..