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AQA AS Physics A Unit 2 25/05/12 - PHYA2

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Original post by Millyshyn
That's absolutely fine then, you'll just lose for QWC.
I think 0.09 is right but I wrote it down to more significant figures than that.

ok cool, erm do you think I will get the marks because I did the first calculation and then it was 0.18 to 2 s.f and then halved it?
Reply 1281
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aerf
Kinda disappointed as some of the waves stuff that came up I wasn't taught and they are nowhere to be seen in my 'Advanced Physics' book that 6form gave me. I think I'm going to buy the AQA Nelson Thornes one for A2
Original post by Kdot
You'll be fine, might get benefit of the doubt if your really lucky, at most you'll probably lose 1-2 marks (2 if you've got a :angry: marker lol).

Umm, yes if you take it to 1 s.f.

do u think i will get the marks for writing it to 1 s.f?
in question 6
for a) i wrote that X has moved from 0 displacement and is moving to maximum displacement
for b) i put both of them as out of phase
for e) fundamental mode
are those right?
Original post by sreddy17
ok cool, erm do you think I will get the marks because I did the first calculation and then it was 0.18 to 2 s.f and then halved it?


Might just get marks for working but there is a possiblity they'll mark your answer right because it would've rounded to 0.09 anyway even if you didn't round early.
Reply 1285
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Kdot
Original post by sreddy17
do u think i will get the marks for writing it to 1 s.f?


Ill get back to you on that in 3 months :tongue:
Original post by Millyshyn
Might just get marks for working but there is a possiblity they'll mark your answer right because it would've rounded to 0.09 anyway even if you didn't round early.


ok cool, thanks dude appreciate it
can someone explain mathematically why the energy stored in series is greater than parallel please?
Original post by AhiTribianni
can someone explain mathematically why the energy stored in series is greater than parallel please?


E=(1/2) x f x extension
Extension was larger in the series system and f was constant so E is greater in series


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Do you reckon I'd get away with gravity instead of weight for the 'forces acting on the helicopter' question?
Reply 1290
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MSI_10
15
Original post by Tanmayee
E=(1/2) x f x extension
Extension was larger in the series system and f was constant so E is greater in series


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What if your value for parallel was larger than that of the series one, so you argue the opposite.. Do you get ECF for that?
Original post by MSI_10
What if your value for parallel was larger than that of the series one, so you argue the opposite.. Do you get ECF for that?


Probably. :smile:


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I thought they said explain without further calculations, i.e. explain qualitatively?
Original post by Tanmayee
E=(1/2) x f x extension
Extension was larger in the series system and f was constant so E is greater in series


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But since there are 2 springs would you not have to consider both extensions so energy stored would be the same?
Original post by Little Wing
I thought they said explain without further calculations, i.e. explain qualitatively?


Yup, they did.


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Original post by AhiTribianni
can someone explain mathematically why the energy stored in series is greater than parallel please?


E=0.5kΔL
Greater total extension in the series springs,
∴ E will be greater (more energy stored)
This could be wrong as it's late and I'm tired :smile:
Original post by AhiTribianni
But since there are 2 springs would you not have to consider both extensions so energy stored would be the same?


It was asking you to compare the two setups, not the individual springs


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Original post by Tanmayee
Yup, they did.


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Oh thank god :P
Reply 1298
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Kdot
Original post by AhiTribianni
can someone explain mathematically why the energy stored in series is greater than parallel please?


The question did say without any further calculations but here it goes,
Energy stored = 0.5xΔLxF where F = W

Energy stored in PARALLEL
Ep = (0.5 x (0.08823529412) x (7.5) ) 2
as there are 2 springs
Ep=0.6617647059J
Ep=0.66J


Energy stored in series
Es = (0.5 x (0.1785714286)x 15)2
as there are also two springs
Es = 2.678571429J
Es = 2.7J


Es approximately 4x greater than Ep. There is more energy stored in the series strings.. ( Es = Energy stored in SERIES arrangement -- Ep = Energy stored in the PARALLEL arrangement)
(edited 11 years ago)
Original post by Kdot
You can never know with these AQA mark schemes, but from the figures you have been given (both are 2.s.f) I dont think you should go any less than 2 tbh, but again i am just like you, I've taken the exam.


I wrote a note on my paper telling them that because all I can see is 2 sf i'm going to use 2 sf. They'd better not be cruel. Nowhere did they use 3sf, even in the moments questions so I rounded up my answers. Hmm. They're just so fussy!

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