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

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    (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
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    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?
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    For work done moving the charge, did anyone use W= Q1Q2/4piE0r??
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    (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)
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    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?
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    (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
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    (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
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    (Original post by 000alex)
    300000 instead of 150?
    OH wut i didn't even notice the 000000,
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    (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
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    (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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    (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?
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    (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.
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    (Original post by 000alex)
    300000 instead of 150?
    OH wut i didn't even notice the 000000, I just doubled R
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    (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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    (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!
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    (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
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    I put Weber Turns as the units...correct or?
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    (Original post by Disney0702)
    How is the first question acceleration.
    Is rate of change of momentum really acceleration?
    Did you put weight?
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    (Original post by Disney0702)
    Grade boundary predictions?
    55 for A*
    50 for A
    etc...
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    (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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