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OCR B: Advancing Physics - G494 (Rise and Fall...) 24/1/2012

Just wondering who's taking this exam and how they feel about it :smile:

How's the revision going?

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Reply 1
I am about to start serious revision soon. When we did all the relativity stuff, my teacher said he was going to teach us stuff outside the course so we would have a fuller understanding... but he didn't say which bits of what he taught we wouldn't actually need. Confusing :frown:
Original post by MsGD
I am about to start serious revision soon. When we did all the relativity stuff, my teacher said he was going to teach us stuff outside the course so we would have a fuller understanding... but he didn't say which bits of what he taught we wouldn't actually need. Confusing :frown:


Was Einstein's theory good? Relatively! :awesome:

... :getmecoat:

Did you get the CGP guide?

AFAIK, all you really need to know about relativity is the equation:
γ=tt0=11−v2c2\gamma = \dfrac{t}{t_0} = \dfrac{1}{\sqrt {1-\frac{v^2}{c^2}}}
where γ\gamma is the relativistic factor, tt is the observed time and t0t_0 is the actual time. We didn't really cover too much extra other than a cheesy video of two spaceships overtaking eachother.

EDIT: oh, and when v<<c⇒γ=1⇒t=t0v << c \Rightarrow \gamma = 1 \Rightarrow t = t_0
(edited 12 years ago)
i hate this course and i hate physics and i dont know how to revise for it and i need to get my blimming A!! :frown:
Original post by pinkprincess123
i hate this course and i hate physics and i dont know how to revise for it and i need to get my blimming A!! :frown:


Well, I can't make you like physics more, but if you get stuck on stuff, I can try to give you a hand :smile:
Reply 5
Thought I'd bump this up, just because this is the exam I'm dreading most. :/ I need to get over 90% in this exam, but I feel like that will be a long stretch.
Original post by croag
Thought I'd bump this up, just because this is the exam I'm dreading most. :/ I need to get over 90% in this exam, but I feel like that will be a long stretch.

I'm aiming for the same - my physics teacher predicted me an A* for UCAS...

I've been getting comfortable >90% on the old spec papers, but the new spec stuff's much harder. :s-smilie:
I can get the june 2011 paper if it would help anyone? Maybe even a markscheme.v
Reply 8
yeah post it please :-)
Reply 9
Original post by Contrad!ction.
Was Einstein's theory good? Relatively! :awesome:

... :getmecoat:

Did you get the CGP guide?

AFAIK, all you really need to know about relativity is the equation:
γ=tt0=11−v2c2\gamma = \dfrac{t}{t_0} = \dfrac{1}{\sqrt {1-\frac{v^2}{c^2}}}
where γ\gamma is the relativistic factor, tt is the observed time and t0t_0 is the actual time. We didn't really cover too much extra other than a cheesy video of two spaceships overtaking eachother.

EDIT: oh, and when v<<c⇒γ=1⇒t=t0v << c \Rightarrow \gamma = 1 \Rightarrow t = t_0


cheers! now its 13 days away and I only get 45% on mocks - it's the B questions I **** up. And I also think we need to know about red shift.
very nervous about this exam D:
want to get an A though, so i'm revising hard!
Something i've found helpful; get together with someone in your class and just talk through the chapters, i find it helps stick in my mind if i'm trying to explain it to someone else!
Original post by MsGD
cheers! now its 13 days away and I only get 45% on mocks - it's the B questions I **** up. And I also think we need to know about red shift.


Yeah, how the wavelengths stretch towards the longer wavelengths as the object becomes more distant due to the doppler effect. I mess up the explanations. Specifically the kinetic theory explanations.

Original post by rachmcg666
very nervous about this exam D:
want to get an A though, so i'm revising hard!
Something i've found helpful; get together with someone in your class and just talk through the chapters, i find it helps stick in my mind if i'm trying to explain it to someone else!


I reckon studying the mark scheme really works, because I'm at a stage where I understand it and just need to use the right words. They tend to be really picky about what they want written down. Also, lol at the location you've got :laugh:
Reply 12
Original post by Contrad!ction.
Yeah, how the wavelengths stretch towards the longer wavelengths as the object becomes more distant due to the doppler effect. I mess up the explanations. Specifically the kinetic theory explanations.




You just say that, as a result of space itself expanding, the wavelengths of light moving through it also will increase.

:smile:

and I actually got 50% on my mock.. improvement!
Original post by MsGD
You just say that, as a result of space itself expanding, the wavelengths of light moving through it also will increase.

:smile:

and I actually got 50% on my mock.. improvement!

Generally, I mess up explanations :tongue:

I'm in the middle of mocks and exams now - my first exam's tomorrow - M2. If you think the mechanics in the physics exam is hard, you should try the mechanics maths modules. Still, a lot more prepared for that now.

My wall's in the process of being covered in physics-related sticky notes.
Original post by Contrad!ction.
Also, lol at the location you've got


i'm liking yours too ;D
what are your marks like on past papers?
Original post by rachmcg666
i'm liking yours too ;D
what are your marks like on past papers?

Thing is, I sound nothing like a farrrrrrmer :laugh:

They're the old spec, which are easier, but ~90%.

My head of 6th (also my physics teacher) wants me to get an A*.
(edited 12 years ago)
Original post by Contrad!ction.
Thing is, I sound nothing like a farrrrrrmer :laugh:

They're the old spec, which are easier, but ~90%.

My head of 6th (also my physics teacher) wants me to get an A*.


yeah me neither but everyone assumes I will when they hear i'm from dorset! :')
ah fair enough :3 i've been getting middle B's, i find physics a little confusing! but i've been predicted an A which i think i can get if i work hard enough :smile:
Something you could help me on; What's the equation for Gravitational Potential? i know it's either -GM/r or -GM/r^2 , but different sources say different equations so i'm extremely confused D: helllllllllllllllp!
Original post by rachmcg666
yeah me neither but everyone assumes I will when they hear i'm from dorset! :')
ah fair enough :3 i've been getting middle B's, i find physics a little confusing! but i've been predicted an A which i think i can get if i work hard enough :smile:
Something you could help me on; What's the equation for Gravitational Potential? i know it's either -GM/r or -GM/r^2 , but different sources say different equations so i'm extremely confused D: helllllllllllllllp!

Well, if you want me to go through anything then quote me in here and I'll give it a go - I quite enjoy helping out and I should be able to explain things. (And if I can't, then I'll look at it and hopefully I'll learn something too! :biggrin:) Also, I want to be a teacher so helping here gives my explanation skills a bit of a challenge.

Vgrav's in the formula book, last page: −GMr\frac {-GM}{r} - in fact, the only spacey equation that isn't is the one for Egrav, which you can deduce from the other three as there are 2 that use GMm, and 2 with r2 - so Egrav must be the one that's not in there - −GMmr\frac {-GMm}{r}. And if you think about it, energy's just potential, multiplied by the mass - check units if you're unsure.

Learn what's not in the formula book, and how to derive the rest. If you forget a formula, look at the units of the things you've been given and the units of what you need to find, and see what you can do to get there. If you've got something in m, and something else in m s-1, you don't need to know that speed = distance / time, because you can get that from the units. Simple example, but as long as you know the equivalent units (W = J s-1, for example) then you can work out an equation from there (like Power = Work Done / Time)
(edited 12 years ago)
Original post by Contrad!ction.
quote me in here and I'll give it a go

So Vgrav is Gravitational Potential & Egrav is Gravitational Potential Energy?
i've got the formula booklet infront of me, which says Vgrav = -GM / r so that's what i assumed it was.
But surely as G.P.E = mgh , g is -GM/r^2?
i worked backwards like this;
G.P.E = -GMM/r = mgh
G.P.E = m(-Gm/r^2)h
- as the h and one of the r's cancels to make the GPE formula.
Sorry if this is confusing. I'm confused. Thanks by the way!
(edited 12 years ago)
http://www.ocr.org.uk/download/kd/ocr_9654_kd_gce_spec.pdf

- just found in the spec (page 38) that g = -Gm/r^2 is the radial component & Vgrav = -GM/r
What's the difference between Vgrav & radial component g?
arrrrgh!

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