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# OCR Physics A Breadth of Physics (24th May 2016) Discussion Watch

1. a mcq about voltage halved what happen to the velocity of the electron
2. I found it a strange paper all in all, I looked at the clock and all my time had gone just as I began to feel like I was getting warmed up. and it seemed very short, probably just lost track of time Pretty sure I failed all/most the calculations I was super stressed out.
3. (Original post by WhizzKidhehe:))
I made some stupid mistakes for multiple choice like the second one: Work done against gravity- I used perpendicular distance thinking it was moments but it was in the direction of force... damn.

But overall, i think Ive done alright, not too bad

I have failed that test so badly! I didn't know how to approach the questions because they weren't making any sense to me. I predict that I got an E
4. For the pressure question with the cylinder was I write to say you can use Newton's third law and so find the cross sectional area and weight of the cyclider and sub that into the pressure equation (force/cross sectional area)?
5. (Original post by RiahDawson)
Does anyone remember the multiple choice uncertainty question? It was like +- 0.1 and +-0.4? What was the rest of the numbers?
i think i put 6.5
6. (Original post by chenhao96)
a mcq about voltage halved what happen to the velocity of the electron
U/root2

Because eV=1/2mu^2

V Proportional to u^2

V is halved so works out as U/root2

That was my reasoning anyway
7. (Original post by sddsfsdafs)
Same, how many silly mistakes do you think you made? I know I made a few marks worth and have probably lost marks elsewhere (e.g. how to get that third mark for the LED question)...
I think I got the LED one completely wrong, I said the threshold voltage was too low and connect it in parallel? I was just guessing at that point
8. (Original post by julesaquilina)
i think i put 6.5
I think that's correct. I put 2.5 because I thought you have to minus the uncertainties when dividing, but it's plus. :/
9. (Original post by Shva)
U/root2

Because eV=1/2mu^2

V Proportional to u^2

V is halved so works out as U/root2

That was my reasoning anyway
I put root2(u) since your answer would give a larger answer wouldnt it? Where as root2 multiplied by u will be smaller??
10. (Original post by sddsfsdafs)
Same, how many silly mistakes do you think you made? I know I made a few marks worth and have probably lost marks elsewhere (e.g. how to get that third mark for the LED question)...
I think I might have lost a mark because I forgot to say the emf for the led maybe was too low. I talked about polarity, maybe I lost a bit in the one about the force on the asteroid because I crossed out the bit where I wrote in the opposite direction but drew a reflection of the graph. A couple multiple choice and forgetting to divide by two for acceleration.mostly only losing one mark ;(. But it was good.
11. (Original post by Shva)
U/root2

Because eV=1/2mu^2

V Proportional to u^2

V is halved so works out as U/root2

That was my reasoning anyway
I picked u/root 2 without any reasoning thought it looked nice to be honest, i hope its correct lool.
12. (Original post by Shva)
U/root2

Because eV=1/2mu^2

V Proportional to u^2

V is halved so works out as U/root2

That was my reasoning anyway
i also find v is proportional to u^2 so when v halved u is root2u
13. (Original post by WhizzKidhehe:))
I got that but now I'm starting to doubt it because it seemed too easy
I thought it was 0.8/0.2 = 4 because it was the ratio between the smaller diameter/the larger one and a thinner wire will extend more so will have greater epe (so it must be greater than 1)
14. Anyone know the total marks for the last 2 questions?
15. I doubt 54 would be an A because it's new spec and also because that would mean it's only two marks less than 80%. When usually an A in physics is around 70. I mean for the practice paper ocr had I got mid 50s which was top three in the year (well performing school) and in the top set class most people averaged 35/70.
16. I personally think depth in physics is gonna be easier not just because of the exam itself but the fact that I have weeks to revise for it. Todays paper I didn't even touch module 4 could only revise module 3. module 4 itself should be a subject alone. I'm pretty confident i got a U today
17. (Original post by voltz)
I put root2(u) since your answer would give a larger answer wouldnt it? Where as root2 multiplied by u will be smaller??
Root2= 1.414

So >1

So I thought itd get smaller? Since its greater than 1?
18. (Original post by chenhao96)
i also find v is proportional to u^2 so when v halved u is root2u
yeah I got the same, I was about to write the 4u but remembered it was the opposite way around
19. For the last question, I didn't point out the polarity of the L.E.D., how many marks do you reckon I'd get for mentioning the e.m.f. being too low so use another cell as well as put the resistor parallel to the L.E.D instead of in series?
20. (Original post by TheHobbit)
I thought it was 0.8/0.2 = 4 because it was the ratio between the smaller diameter/the larger one and a thinner wire will extend more so will have greater epe (so it must be greater than 1)
didn't the equation they give have thinner wire on top?

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