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# AQA A-Level Equations that aren't given watch

1. What are the equations we need to remember for the AQA A2 exam that aren't on the formula sheet?
2. There are actually quite a few, and to be honest I don't think I can list them. I can however say that you do need to know the derivations of some formulae, and I have been told to learn the ins and outs of these:

- SHM formulae (every last one, even the weird fruity looking energy equation that relates amplitude and such)
- Kinetic theory formula (p = (1/3)*density*c^2... I'm just going to go derive that one now :-
- Circular Motion v^2 / r formula

All the above three are formula derivations that seem to have popped up in questions on my past papers or IAL past papers, and it appears as though they don't directly require derivation but instead require usage at a step of the derivation, i.e. rather than using the formulae given on the sheet you must take a step back and utilise a different method.

I'll ask my teacher on Monday to see if she could make a formula sheet or tell me some, or perhaps someone else may provide them :P
3. Make sure you can rearrange the formulae for exponential decay (radioactive half life & capacitors)

formula sheet gives you
Q=Q0 e-t/RC *
which rearranges to
ln Q - ln Q0 = -t/RC
which is likely what the questions will need
4. there are quite a few , the pressure one which is derived from the kinetic theory model: P=NMU/V and there are 3 variations of this which can also be derived : P=1/3NMC^2 , and one more which is when you take the C^2 and replace it with C(rms)
There is also a Gravitational frields formula for orbits , the T^2=4(pi)^2*R^3/GM which is derived from V=2(pi)R/T and V=Squarerootof(GM/R)
In addition there are a few more circular motion equations:V^2/R , also Angular speed=angle/t
There are a few capacitors equations too which i cannot remember , but one is Timetohalf=0.69RC , and a few for Charging and discharging which are not given.
you also don't get given the stopping potential of an electron , in the photo electric effect stopping potential=KE/charge of electron
the escape velocity of an orbit is not given: v=squareroot(2GM/R)

there a few more which i do not remember of the top of my head , but hope this helps
5. I'm doing the AQA syllabus as well and just for A2 I've found
Capacitors topic:
• I=I0e-t/RC
• V=V0e-t/RC

Gravitational fields topic:
as above, escape velocity

Nuclear physics:
• A=A0e-(wavelength)t where A is activity
• C=C0e-(wavelength)t where C is count rate
• (this isn't really an equation just a method that'll definitely want to remember for this topic) M defect= Zmp + (A-Z) mn - Mnuc (..where M is mass)

I've also seen a question that requires some vague knowledge that intensity is equal to power per unit area or I=P/A
I find that equations not given tend to pop up in multiple choice more often than actual calculation questions so it'll be best to memorise them so you can get through multiple choice faster at the end of the paper.
This doesn't include all the derivations you need to learn.

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