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# OCR Physics G484 - June 2013 Unit 4 (OFFICIAL RETAKE THREAD) Watch

1. I think we shouldn't discuss this until midnight?
2. (Original post by sj_1995)
I got 1.5 x10^7...
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Ohhhhhhh I did wrong I still do not know how to do that...
3. Mmmmmmm nice easy paper to finish off how did u others find it

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4. (Original post by etmkndmpl)
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Ohhhhhhh I did wrong I still do not know how to do that...
I figured out how many moles of air was added using the data they gave you, added it to the moles we had worked out earlier in the question, they did pV=nRT with my new number of moles on the system
5. (Original post by sj_1995)
I figured out how many moles of air was added using the data they gave you, added it to the moles we had worked out earlier in the question, they did pV=nRT with my new number of moles on the system
On
6. I found it a nice paper. The only weird question was: 'Describe the Earth's gravitational field close to the surface of the Earth' (2 marks). What would they have wanted for that?
7. (Original post by Gulzar)
On
The air was being added in to the fixed volume of 0.05m^3. I think we were given the volume of the air added only to work out the added number of moles using n=pV/RT
8. (Original post by Gulzar)
On
The air was pumped into the same cylinder of volume 0.05m^3. So you use that volume.
9. Anyone fancy guessing the grade boundaries? My guess is: 53 for A*, 47 for A, because it was a nice paper. No tricky calculations (bar the last question, arguably) or long describing questions.
10. (Original post by Edmundith)
I found it a nice paper. The only weird question was: 'Describe the Earth's gravitational field close to the surface of the Earth' (2 marks). What would they have wanted for that?
I basically described them as being (virtually) parallel as the earth is a very large sphere, and evenly distributed.
Still, I waffled on about how technically they would be more dense in some areas depending on the density of the earth below.

I do agree it is a bit of an odd question.
11. salaam what did you guys get fr the change in contact area
12. i did same i put that the lines were parrallel to each other and perpendicular to the surface of the earth
13. (Original post by aharvard)
I basically described them as being (virtually) parallel as the earth is a very large sphere, and evenly distributed.
Still, I waffled on about how technically they would be more dense in some areas depending on the density of the earth below.

I do agree it is a bit of an odd question.
I mentioned they'd be very nearly parallel and directed at the Earth's centre of mass. Probably got 1 mark. I thought of 'evenly spread/equal strength' just as the papers were being collected in! So I couldn't write it...
14. What did you guys get for pressure at the end, may've done it wrong as it was 4 marks, I got something like 4*10^5 Pa
15. (Original post by Edmundith)
I mentioned they'd be very nearly parallel and directed at the Earth's centre of mass. Probably got 1 mark. I thought of 'evenly spread/equal strength' just as the papers were being collected in! So I couldn't write it...
I said equal magnitude and equally spread field lines too, but I'm thinking they're looking for something else aswell.
What did you guys get for pressure at the end, may've done it wrong as it was 4 marks, I got something like 4*10^5 Pa
I got a really nice answer out: P = 1.5E^(something) Pa, exactly.
17. So what's the general consensus? Hard, ok or easy? Any ideas about grade boundaries?
18. i got 1.5x10^7
19. Well all my lot have just come out smiling. pretty straightforward.
Only tricky bits were 3a) 4b) and 6bii.
What did you guys get for pressure at the end, may've done it wrong as it was 4 marks, I got something like 4*10^5 Pa
don't know what i got but I worked out the moles of the added gas using pv=nrt then added them on to the original moles, then worked out the pressure again

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Updated: December 13, 2013
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