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# AQA MOd 4 IMPOSSIBLE watch

1. ahahahaahahahhahaahha I got different answers to ALL of those I aM aN iDiOt

i got
1-smallest acceleartion(at the bottom its constant speed not accelrating?)
6-new gravity 16g(i did a calculation and calc said 16 )
9-work done/something like that??
12-p falls q falls
15-matching graph because e=N flux and n is constant so graph must be in proportion- doesn't that mean it has the same shape?
2. Looks like I managed not to read the part that said 2nd order and just thought it was first. Doh!
3. Ahhh i see what i did, forgot to square root
bugger.
4. (did you have to say earth days!? )
I'm guessing so. I don't remember the Mercury day being on the syllabus. Oh and I did, in fact, get 24mm, not 40mm, I don't know why I said 40mm.
5. 1-smallest acceleartion(at the bottom its constant speed not accelrating?)
No, it's at its greatest further away. If you look at the acceleration equation on the data sheet you'll see that acceleration is directly propertional to x, the displacement.
6. (Original post by ryan342)
I'm guessing so. I don't remember the Mercury day being on the syllabus.
lol
(Original post by ryan342)
Oh and I did, in fact, get 24mm, not 40mm, I don't know why I said 40mm.
phew

Any thoughts on Section B; for the explanation in question 1 I went with the formation of a stationary wave and certain depths of water (which I thought would speeed the sound wave up) giving an antinode at the top of the column of air... As for getting a solveable equation in part ii)

For question 3 on capacitors, the graph was a straight line through the origin with a gradient equal to 1/capacitance and I said that the area under the graph was equal to the energy stored by the capacitor. Then you had to work out the two voltages; I got 6V when it was discharging through the first RC for 26 seconds and then roughly 2V when it was discharging through the 0.5RC for the next 14 (40 - 26...) seconds. My graph was therefore an exponentially decreasing graph where the gradient increased at 26s...

Cheers
7. (Original post by deity47)
Come to think of it, that is the exact calculation I did:
4/20 * 120 = 24mm
I think that from reading the start of the thread I got brainwashed that I put 40mm! I did in fact mean 24mm.

Mmmmm just looking at that one... does that work when they are both charges at a points?

I did

4/x = 16/(0.12-x) (from Q/(r*4*pi*that squigly sideways ω ), everything other than Q/r cancels)
0.48 - 4x = 16x
x = 0.48/12 = 0.04m = 40mm
8. (Original post by deity47)
lol
phew

Any thoughts on Section B; for the explanation in question 1 I went with the formation of a stationary wave and certain depths of water (which I thought would speeed the sound wave up) giving an antinode at the top of the column of air... As for getting a solveable equation in part ii)

For question 3 on capacitors, the graph was a straight line through the origin with a gradient equal to 1/capacitance and I said that the area under the graph was equal to the energy stored by the capacitor. Then you had to work out the two voltages; I got 6V when it was discharging through the first RC for 26 seconds and then roughly 2V when it was discharging through the 0.5RC for the next 14 (40 - 26...) seconds. My graph was therefore an exponentially decreasing graph where the gradient increased at 26s...

Cheers

I went on about constructive and destructive interference for that first one, wanted to write something about stationary waves but couldnt think of anything to write to get 4 marks. Decided to leave it as it was as I didnt have much time left but Im unlikely to get any marks I think!

Got the same looking answers for Q3, think it was 6.06 and 2.9ish. I tried to do the graph like 2 seperate exponential curves (on for 0-26 and another from 26 onwards), but my drawing skills failed me miserably and they ended up looking like the same curve
9. Hi davedave Your method would have worked but i believe you made an error at
(Original post by davedave)
0.48 - 4x = 16x
x = 0.48/12 = 0.04m = 40mm
where it should be:

0.48 - 4x = 16x
0.48 = 16x + 4x = 20x *not 12x*
0.48/20 = 0.024m

Similarly as you said Q/r should give the same value for the two charges:
4/40 = 0.1
16/(120-80) = 0.2
On the other hand,
4/24 = 0.16
16/(120-24) = 0.16

(Original post by davedave)
my drawing skills failed me miserably and they ended up looking like the same curve

deity47
10. Another doh! I hate silly errors!
11. (Original post by deity47)
lol
phew

Any thoughts on Section B; for the explanation in question 1 I went with the formation of a stationary wave and certain depths of water (which I thought would speeed the sound wave up) giving an antinode at the top of the column of air... As for getting a solveable equation in part ii)

For question 3 on capacitors, the graph was a straight line through the origin with a gradient equal to 1/capacitance and I said that the area under the graph was equal to the energy stored by the capacitor. Then you had to work out the two voltages; I got 6V when it was discharging through the first RC for 26 seconds and then roughly 2V when it was discharging through the 0.5RC for the next 14 (40 - 26...) seconds. My graph was therefore an exponentially decreasing graph where the gradient increased at 26s...

Cheers
for the water wave thing i said the amount of water causes diffraction and waves constructively interfere making the sound more intense as the amplitude is increased. For the equations I treid dsinØ=nλ where n is 1, and d was the difference between the lengths, but i stil eneded up with two unkowns and gave up.
I got the grad to be 1/c and area under i put energy stored to the first part i got 6V and second i got around 3V and if 0 is 12V mine was a straight line..., i did do the next 14 seconds seperate.
12. got the same for nearly all apart from 7 and 15. on 15 i put the same graph as the E one as it is proportional to it.
yes, thats what i put for 15, because i think its faradays law, which states that it is directly proportional, so i didn't see how it could be a square graph
13. Faradays law states that it is proportional to the change in flux. Hence emf is induced when the flux changes, therefore the square graph. Thats what i thought anyway!
14. (Original post by gemm)
yes, thats what i put for 15, because i think its faradays law, which states that it is directly proportional, so i didn't see how it could be a square graph

I did the square graph because I thought the emf produced is proportional to the change in flux. The graph of flux had 3 flat parts (no change in flux) and 2 parts where the flux was changing at a constant rate, so produces a constant emf. One of the 2 changing flux parts had a steeper gradient than the other, so faster change in flux and higher emf produced than the other.
15. I did the square graph because I thought the emf produced is proportional to the change in flux. The graph of flux had 3 flat parts (no change in flux) and 2 parts where the flux was changing at a constant rate, so produces a constant emf. One of the 2 changing flux parts had a steeper gradient than the other, so faster change in flux and higher emf produced than the other.
i didnt think about it like that, its only one question anyway
16. Agreed! Square form graph with bigger "square" first due larger gradient ..
17. (Original post by gemm)
i didnt think about it like that, its only one question anyway
but you never know that 1 mark could be the diferenece between a B and an A, just to be annoying. or if you did really poorly a U and a E
18. but you never know that 1 mark could be the diferenece between a B and an A, just to be annoying. or if you did really poorly a U and a E

thx for reminding me about that
don't you get two marks for every correct multiple choice ?
19. (Original post by gemm)
thx for reminding me about that
don't you get two marks for every correct multiple choice ?
not sure possibly, Did it say 30marks for section A, hmm I think it did actually. maybe you only get one if you do that change your mind thing, but you get 2 if you get it right without crossing out lol
20. The paper was definitely the hardest one I've done. I managed to squish so many careless errors onto that one lil sheet.. BOO! But I *think* module 5 possibly averaged out the badness.

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