you need to knoe them all...if u look at the syllabus it states
'...dry cell or lead-acid cell and evaluate it in comparison to: - button cell..."
it says compare it ti all of them...but you only have to do one of them not both....they must say dry or lead acid...our teacher made this clear...
what are you a talking aobut...you can use physics in math, thats where they deerive the three and four unit formulas from...integration.
its quite simple to do it from first principles..
v=u+at
at peak of the vertical component final velocity is equal to zero
therefor 0=u-gt...
Dont use 3 unit, it should be fine, but if it is a few marks worth you will not score the one for applying the correct formula, which is part of the syllabus.
Good luck everyone.