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

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Original post by Mehrdad jafari
Yeah, that's a good idea but it would be better knowing the questions too :frown:


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It would definitely be good to have a copy of the questions yeah! If I don't write my answers down I won't remember what I put anyway.
Original post by JJBinn
I think the 'method' for this is to work out a lowest common factor but I don't really get that.

I've learnt that you can use the difference in time period, then divide the smaller of the two periods by the time difference. This will give you the amount of oscillations the longer period needs to do before they are in phase again.


It seems like its a given that they're only in phase at the beginning of the oscillation but I can't work out why it won't happen throughout the cycle?

In future though I can just work it out by finding when they both have gone through an integer number of oscillations?
Original post by Lau14
It would definitely be good to have a copy of the questions yeah! If I don't write my answers down I won't remember what I put anyway.


True. I think even writing the answers would remind us of the questions, maybe


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Original post by Mehrdad jafari
True. I think even writing the answers would remind us of the questions, maybe


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Probably not for the MC because they're just letters!
Last year people came out with a list of their answers, I'm not sure if they wrote it on their formula booklet during the exam or something but I'd worry about it looking suspicious.
Original post by ShutUpLegs
Last year people came out with a list of their answers, I'm not sure if they wrote it on their formula booklet during the exam or something but I'd worry about it looking suspicious.


You can't even take the formula sheet, that's the problem.


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Original post by Mehrdad jafari
You can't even take the formula sheet, that's the problem.


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I don't know how they did it then. I wouldn't write on anything that I had brought into the exam myself for obvious reasons.

Between us last year we managed to remember all the Section B questions but I think people just compared what letters they had for the multiple choice.
Original post by ShutUpLegs
I don't know how they did it then. I wouldn't write on anything that I had brought into the exam myself for obvious reasons.

Between us last year we managed to remember all the Section B questions but I think people just compared what letters they had for the multiple choice.


The place we are taking exam is quite small and people are just walking around at all time otherwise i try to write the answers(not letters) on the formula sheet and see if i can take it out. If you guys didn't hear from me after the exam then assume I got disqualified lol


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Original post by Lau14
I was thinking of just writing the letters down on my calculator if I get the time, so I've at least got something to compare, even if it's not very helpful without the questions. Can't get hold of the paper though unfortunately :/


I might do the same. Although we won't know why they differ :L praying someone can take the paper home with them. Otherwise we'll have to just debate random MC questions in any order and the answers people got for them.


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Original post by CD223
I might do the same. Although we won't know why they differ :L praying someone can take the paper home with them. Otherwise we'll have to just debate random MC questions in any order and the answers people got for them.


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Actually I think this is the way they did it before, will do this if I have time.
Original post by CD223
I might do the same. Although we won't know why they differ :L praying someone can take the paper home with them. Otherwise we'll have to just debate random MC questions in any order and the answers people got for them.


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It's almost impossible taking them from the exam hall :frown:

Edit: unless you take yours

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(edited 8 years ago)
Original post by Klaxoii
And this question, ImageUploadedByStudent Room1433883749.672109.jpg


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Just took me ages to work out... There must be a quicker way.....

I just used v= root (E/0.5C)
Then plugged in values for initial energy with capacitance a) then the lower energy with capacitance a) and saw that v wasn't 2v less.
Then I repeated for capacitance b) and it was!!


That probably makes NO SENCE whatsoever... Physics is hard to explain in writing
Can anyone help?

ImageUploadedByStudent Room1433885738.082562.jpg


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Original post by ShutUpLegs
It seems like its a given that they're only in phase at the beginning of the oscillation but I can't work out why it won't happen throughout the cycle?

In future though I can just work it out by finding when they both have gone through an integer number of oscillations?


They will always be at different points in their cycles until they reach the certain time that you are asked. This is because they have different periods, so the one with the longer period will be slightly behind the shorter period one for a number of oscillations before the other one will gain enough such that it is one oscillation ahead and again in phase. If that makes sense.
Original post by Sbarron
Just took me ages to work out... There must be a quicker way.....

I just used v= root (E/0.5C)
Then plugged in values for initial energy with capacitance a) then the lower energy with capacitance a) and saw that v wasn't 2v less.
Then I repeated for capacitance b) and it was!!


That probably makes NO SENCE whatsoever... Physics is hard to explain in writing


CD had a nice workout in the form of a picture for that one


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How about if we write the units down, would that remind us of the question?


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Original post by Mehrdad jafari
CD had a nice workout in the form of a picture for that one


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Ah well he had the right idea then!
Original post by thedon96
Hey, I know the q wasn't directed to me but this really helped:
http://www.cyberphysics.co.uk/topics/magnetsm/electro/Transfromer/trnsfrmr.htm


thanks mate!
By the way guys how do you approach your sig figs in the papers? I never know whether to use my rounded answer in further calculations or to use the full answer but I often have a slightly different value to the mark scheme :/

I usually give the answer to the first part to the sig figs in the question, should I use that value in the next parts or use the unrounded one?
can anyone help me on the MCQ Jan 2013 paper question 9. Two pendulums P and Q are set up alongside each other. The period for pendulum P is 1.90s and for Q is 1.95s. How many oscillations are made by pendulum Q between two consecutive instants where P and Q are moving in phase with one another.

thanks in advance
x

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