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# AQA PHYB4 Jan 28th 2010 watch

1. (Original post by mouldy)
i personally thought it was ok. lots of people in my school found it very hard though. i was very surprised at one of the x ray questions. about calculating the internal energy of the anode. i used E= IVt which i found in the as formulas. did anyone else do this? i had never seen a question like that before!
Ooh, I used P=IV because the units were J/s which is the same as Watts if I remember correctly but that question was annoying...it said that it was 0.6% efficient, so i assumed that 99.4% of the 90kV was used as inefficient heat transfer but i think i may have over complicated things
2. (Original post by n_251)
Ooh, I used P=IV because the units were J/s which is the same as Watts if I remember correctly but that question was annoying...it said that it was 0.6% efficient, so i assumed that 99.4% of the 90kV was used as inefficient heat transfer but i think i may have over complicated things
yeah you could use p=iv one of my friends did. because e/t = p. it sounds like we have done similar thing though which is good. the only question i had no idea really what to do was the one near the end where you had to draw a graph. but hopefully i will of got 108+ ums to stay on track for the a* what are you hoping for?
3. (Original post by mouldy)
yeah you could use p=iv one of my friends did. because e/t = p. it sounds like we have done similar thing though which is good. the only question i had no idea really what to do was the one near the end where you had to draw a graph. but hopefully i will of got 108+ ums to stay on track for the a* what are you hoping for?
oh for the graph of force against time? i thought it would have just been an accelearation graph since F=ma (so the mirror reflection of the displacement graph they gave) but then I realised that the force was only applied at one end so that confused me

I'd like an A* but I'd be happy with an A. I "only" need an A in Physics for my offers...an A* would help but I think it will be easier for me to get in my other subjects. I'm just relying on the little buffer I've built up from AS to carry me through this but you never know...most people I sat it with had mixed feelings about it. Some said it was hard, others said it was easy to make mistakes, one guy even missed out about 20 marks and he is meant to be on the clever ones!
4. Bah I thought it was terrible. I felt so unprepared going in and all the questions I found hard to answer. Besides the first few.

Definately an E or a D.. Retake I think.
5. I randomly used P=I^2R, the other equation E=VIT I have never seen in my life. What a fail. The question about national and international security WTF I wrote weapons and bombs, what else can metal detectors be used for?
6. (Original post by mcp2)
I randomly used P=I^2R, the other equation E=VIT I have never seen in my life. What a fail. The question about national and international security WTF I wrote weapons and bombs, what else can metal detectors be used for?
lol I wrote weapons in airports, etc. and then I wrote to detect for knives in schools, as I'd heard this story before!

Damn looking back, I could have said to look for metals or something underground!
7. Main features of a liquid propellant rocket, what were they?
8. (Original post by mcp2)
Main features of a liquid propellant rocket, what were they?
That confused me as I wasn't sure what they were asking about - the fuel or the rocket!

I just said stuff like the payload, exhaust, etc.
9. Well I thought they meant the fuel! So I wrote nozzle, oxidiser tank, combustion chamber and cooling jacket :/
10. hey guys do you remember what you got for the magnet question, because i got 0.01 volts which didn't seem right but i just couldn't work out what i had done wrong. I used NBA/t, for area i did pi x r^2, they gave you the number of turns and also i think they gave you B/t. so i muliplied al lthose values together, and also by 0.15 as it was 15% efficient. is this working out flawed?

Explain why multistage rockets are inefficient?
wtf? i thought multi-stage rockets were efficient, that question really stumped me...
11. (Original post by ollie_91)
hey guys do you remember what you got for the magnet question, because i got 0.01 volts which didn't seem right but i just couldn't work out what i had done wrong. I used NBA/t, for area i did pi x r^2, they gave you the number of turns and also i think they gave you B/t. so i muliplied al lthose values together, and also by 0.15 as it was 15% efficient. is this working out flawed?

Explain why multistage rockets are inefficient?
wtf? i thought multi-stage rockets were efficient, that question really stumped me...
agreed with both points

I got the same answer as you and thought that multi-stage rockets were meant to be efficient
12. (Original post by n_251)
agreed with both points

I got the same answer as you and thought that multi-stage rockets were meant to be efficient
haha that's a relief we can't both be wrong
13. (Original post by ollie_91)
haha that's a relief we can't both be wrong
i just circled the (in)efficient and went on to write some sort of crap but that question got the better of me too
14. (Original post by dull)
i just circled the (in)efficient and went on to write some sort of crap but that question got the better of me too
Exactly, I saw it and everything I had learnt has been about them being efficient. I just went on to say that they weighed more therefore they'd need more fuel to reach escape velocity and they were just carrying dead weight, etc and how the fuel/mass ratio was a vicious circle. Mofos, AQA, all of them.
15. Anyone By Anychance Able To Put The Paper Up?
Help Appreciated.

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