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

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    (Original post by Mattyhouse)
    Are we allowed Graphics calculators in the physics exams?
    why would you need one?
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    (Original post by AR_95)
    Don't ever think that with MC. It can vary from plugging into an equation without doing any work, to 3 or 4 step questions
    well atleast I learnt that now and not in the exam
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    (Original post by gcsestuff)
    Thanks mate is there ever a unit kgms-2


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    Yes, rate of change of momentum (Also known as force)/
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    (Original post by Mattyhouse)
    Are we allowed Graphics calculators in the physics exams?
    Yes
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    Yeah I totally get the part where emf is max at 90 to field/flux lines as they are perpendicular and more are being cut.... But to me that is the same as maximum flux linkage as it's where the most flux is being cut!But I obviously can't see the difference between maximum flux linkage and maximum flux apart from the number of loops are considered!???!And maths explanations won't help I don't do alevel maths and didn't do GCSEs for years so Ihave only leant the basic physics maths skills[/QUOTE]

    It's not really about whether you are doing maths or not. I'm doing a level maths too but i still haven't applied that maths anywhere in physics. The maths does help but that's where we have an idea of what's going on and not where we have no idea, lol


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    (Original post by davidharris96)
    May have been answered, Is the answer B?
    yeh
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    Hi, quick question, if anyone could answer it for me, it would be a great help!!
    Why in a MS does it say E proportional to V squared in the equation of energy stored in a capacitor? Why can't you use V is proportional to E because of the equation: E=0.5QV? How do you now what equation to use when working out what is proportional to what in the energy equations?



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    (Original post by samlyon)
    Anyone? I'm just confusing myself
    The natural frequency is 1.5Hz.

    When the frequency of the driver is equal to the natural frequency 2)(b)(ii), the phase difference is pi/2, i.e. in phase with velocity. At 0.2Hz (i), the phase difference is nearly zero. At 10Hz(iii) the phase difference is nearly pi

    In general:
    when driven at freq much lower than natural: little or no phase difference
    when driven at resonance: phase difference pi/2
    driven at frequency much higher than resonance: phase difference approaching pi.

    I'm afraid I can't explain why this is the case, so unless someone else can it's just something to blindly accept.
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    (Original post by AR_95)
    why would you need one?
    you wouldnt, just saves time with solving quadratics ( i assume this is why he wants to know )
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    (Original post by Brianna96)
    Hi, quick question, if anyone could answer it for me, it would be a great help!!
    Why in a MS does it say E proportional to V squared in the equation of energy stored in a capacitor? Why can't you use V is proportional to E because of the equation: E=0.5QV? How do you now what equation to use when working out what is proportional to what in the energy equations?



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    because technically if the pd is changing so is the charge, its only the capacitance tthat remains constant
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    (Original post by AR_95)
    why would you need one?
    My normal calculator keeps going on and off, its ****ed :s not sure whether just to use my graphic instead ;/
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    How to work out when a set of swings of varying time period will next be "in conjunction"?
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    (Original post by Whateverisbest)
    Think about moving a spring very slowly. You'd barely be affecting the oscillations which is what its getting at with 0.2 Hz.

    1.5hz is resonance as its the same as the natural frequency.

    As for 10Hz, you must remember those resonance curves, right? Think of what happens to the amplitude as the driver frequency exceeds the natural frequency.

    Edit: I didn't pay attention to your question. When in resonance , the driver and the displacement of the oscillation system are 90 degrees out of phase. It's just a fact.
    Thanks, that helps. To confirm for the 0.2 Hz do you assume the effect is so little it's in phase because the mark scheme says in phase with driver
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    (Original post by CD223)
    Which board? AQA C4 screwed me over 😭


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    Yes same AQA, I honestly think for the questions they gave us it was really difficult to get them all done in 90 minutes. I panicked and made so many silly mistakes, was aiming for an A* this year
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    (Original post by Lau14)
    Yes
    Cheers
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    (Original post by Humza Ali)
    How to work out when a set of swings of varying time period will next be "in conjunction"?
    Do you mean when they'll next be in phase? Do the time period difference multiplied by the smallest time period, this gives the number of the smallest time periods that take place, then you multiply by the time period to get the overall time
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    Guys are we allowed to write on the Section A multiple choice question paper so that we can do the calculations?

    Also is it okay to underline words in the questions?

    I never did these things just in case until now that I feel the need to, for this exam.
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    (Original post by HenryHein)
    The natural frequency is 1.5Hz.

    When the frequency of the driver is equal to the natural frequency 2)(b)(ii), the phase difference is pi/2, i.e. in phase with velocity. At 0.2Hz (i), the phase difference is nearly zero. At 10Hz(iii) the phase difference is nearly pi

    In general:
    when driven at freq much lower than natural: little or no phase difference
    when driven at resonance: phase difference pi/2
    driven at frequency much higher than resonance: phase difference approaching pi.

    I'm afraid I can't explain why this is the case, so unless someone else can it's just something to blindly accept.
    Yeh that makes sense I was just trying to work out the exact phase differences for the 0.2Hz and 10 Hz ones but I didn't need to
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    (Original post by Brianna96)
    Hi, quick question, if anyone could answer it for me, it would be a great help!!
    Why in a MS does it say E proportional to V squared in the equation of energy stored in a capacitor? Why can't you use V is proportional to E because of the equation: E=0.5QV? How do you now what equation to use when working out what is proportional to what in the energy equations?

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    It's because Q is dependent on V or something I think?

    (Original post by Mattyhouse)
    My normal calculator keeps going on and off, its ****ed :s not sure whether just to use my graphic instead ;/
    Take both if you want them!
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    What's the difference when dropping a magnet through a copper tube and a coil, if there is any?
 
 
 
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