Using formulae

[dekoyl]

I've noticed towards the latter part of the chapter review, the Jacaranda questions of projectile motion have a lot of working out.
It seems as if their methods were used on the exam, the question would be worth ~4 marks.
What they did in 10 lines could have been found by a simple range = .

Are formulae like this okay to use in the exam? I'm not familiar with the exam structure so I'm not sure.

Thanks

[TrueTears]

Yea, it's perfectly fine to use that formula in some cases. I remember several questions, they had huge workings for some really simple questions. As long as you set out your working I don't see why you can't use a short working method.

[nicholasysc]

emm... Can I ask where you derive that formula from? XD

[dejan91]

Be careful, pretty sure that formula for range only applies to projectile motion in which the projectiile begins and ends at the same height.

[Mao]

Be careful, pretty sure that formula for range only applies to projectile motion in which the projectiile begins and ends at the same height.

yes.

The range formula and those are technically 'not in the course', the exams are written with this in mind, and generally do not include questions that require ridiculous working out with few marks [usually when that happens, you know you've taken the long way].

Another thing is, because of this technical 'not in the course' status, if the final answer is wrong, you will not get method marks. This is the same across maths as well, using a method beyond the course is accepted, but if you get the answer wrong it means nothing can be awarded for workings out.

[dekoyl]

I'm pretty sure I've asked this before but I can't seem to find it so here it is again:

In physics, is it okay to just have a "give answer to 2 decimal places" idea in mind when working through questions (as opposed to chemistry where you have to adjust your significant figures)?
On the last SAC, I gave my answers to 2 d.p. but the teacher said it was unnecessary. Should I just keep at it to be safe (for accuracy reasons if the next part of the question happens to use the previous answer).

Thanks

[Mao]

usually 3 sig figs, but it doesn't really matter.

[TrueTears]

Yeah our teacher said it's best to give all answers to 2 d.p unless they state how many d.p's is required.