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# AQA Physics PHYA4 - Thursday 11th June 2015 [Exam Discussion Thread] watch

1. (Original post by Disney0702)
I believe i got 12N as well
I think I just did mv^2/r = T because its horizontal and weight is verticle. Can't remember what value I got
2. For the question where we used the graph to calulate things, for the first question I used the graph to show is was 30nC...for the next parts I just used forumulae to calculate, and didn't use the graph, can I still get the marks?
3. For work done moving the charge, did anyone use W= Q1Q2/4piE0r??
4. (Original post by Disney0702)
I believe i got 12N as well
Well the motion is horizontal so weight is NOT included.

Vertical components and horizontal components are independent (we learned this is AS Unit 2)
5. What did people put for the iron core coil thing? I just put all I knew about induced emf and what not but I don't think that was even the case?
6. (Original post by fruity97)
I got 15N at first for tension! But I remember changing it towards the end to 12N because I didn't include the weight I think? Stil not sure which is right but they said horizontal so I changed it
It was rotated horizontally so weight is perpendicular to centripetal force therefore ignored

T = mv^2/r 0.25 x 8.6^2 / 1.5 = 12.3N
7. (Original post by NEWT0N)
No time period isn't affected because it only depends on the length of the spring and a simple pendulum is isochronus.

I put the time period stays the same and there is a larger restoring force because the weight is greater at maximum amplitude so the horizontal compoent of weight (restoring force) is larger. But then I went on to say something silly like how this causes a smaller amplitude, but I think it should be a bigger amplitude? My thinking is still a bit cloudy after the exam so I'm hoping someone can clarify this for me!

Re-read what i put. I didn't say that t was affected by m.... I meant that t wasn't affected and therefore no damping because for damping to occur t would be affected
8. (Original post by 000alex)
OH wut i didn't even notice the 000000,
9. (Original post by QueNNch)
What did people put for the unit of flux linkage?
I couldnt remember so I just used the formula BA and wrote unit as Tm^2 (Tesla metre squared).
Wb turns
10. (Original post by Hexaneandheels)
For the question where we used the graph to calulate things, for the first question I used the graph to show is was 30nC...for the next parts I just used forumulae to calculate, and didn't use the graph, can I still get the marks?
Yeah I didn't know which was right to do either, guess they'll award marks for both

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11. (Original post by Mehrdad jafari)
Here are my answers. The ones I'm not sure with i have mentioned next to them.

I have failed to take the answer of one of the MC questions. Let me know if you found which one.
I would be very happy if you could correct the ones that are not right
Attachment 425411

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How is the first question acceleration.
Is rate of change of momentum really acceleration?
12. (Original post by Fred Cantoni)
I put 2.2x10^10 cause the total number of electrons would be 4.4x10^10 but half would already be on that plate, and the other half moves over from the other plate when they're is a potential difference? Anyone confirm or deny this?

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Ahh i think you may be right.
13. (Original post by 000alex)
OH wut i didn't even notice the 000000, I just doubled R
14. (Original post by Disney0702)
How is the first question acceleration.
Is rate of change of momentum really acceleration?
No. It's force.

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15. (Original post by QueNNch)
Well the motion is horizontal so weight is NOT included.

Vertical components and horizontal components are independent (we learned this is AS Unit 2)
Damn!
16. (Original post by Will177)
I think I just did mv^2/r = T because its horizontal and weight is verticle. Can't remember what value I got
I think thats wrong because the weight of particle is not taken into account. I did T - mg = mv^2/r
17. I put Weber Turns as the units...correct or?
18. (Original post by Disney0702)
How is the first question acceleration.
Is rate of change of momentum really acceleration?
Did you put weight?
19. (Original post by Disney0702)
55 for A*
50 for A
etc...
20. (Original post by Will177)
OH wut i didn't even notice the 000000,
This is an unfair advantage for you then, because if they decide to mark it as "150 ohms" then people who got confused by the "150 k ohms" will maybe have drawn a different current intercept due to the confusion. So they would have to mark it like this I think:

Any current less than the original current should get the first mark

Shallower gradient gets the second mark

Anyone agree?

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