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A2 Physics Unit 4 and 5 Revision Thread

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    (Original post by jgmuzic)
    Hi, was wondering if anyone could help me out on a small question - unit 4 aqa, multiple choice.

    When the length of a simple pendulum is decreased by 600mm, the period of oscillation is halved. What is the original length of the pendulum?

    A-800mm
    B-1000mm
    C-1200mm
    D-1400mm

    I don't do maths for a level, as you might have guessed. Is this something to do with proportions or rearranging the simple pendulum equation?
    Any feedback is appreciated.
    The answer is A.

    We know that T=\frac{1}{2}To To = original period of oscillation.
    We also know that L = Lo -600x10^-9 Lo = original length.

    So T = \frac{1}{2}To = 2\pi\sqrt {Lo-600x10^-3/g}

    We also know that To =2\pi\sqrt {Lo/g} = 4\pi\sqrt {Lo-600x10^-3/g} \Rightarrow

    \frac{1}{2}\sqrt {Lo-600x10^-3/g} = \sqrt {Lo/g}
    \Rightarrow


    \frac{1}{4}\frac{Lo}{9} = \frac{Lo-600x10^-3}{9} \Rightarrow

    \frac{1}{4}Lo = Lo - 600x10^-3 \Rightarrow 600x10^-3 = \frac{3}{4}Lo

    Lo = 0.8m = 800mm
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    Does anyone have any good notes for relativity? I'm doing AQA Unit 5 with turning points in physics. And none of the revision guides seem to have detailed enough explanations.
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    Hey, this should help for the relativity stuff...
    Attached Images
  1. File Type: pdf Turning Points - Special Relativity.pdf (586.9 KB, 365 views)
  2. File Type: pdf Exam Style Questions.pdf (837.3 KB, 850 views)
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    does anyone has A2 physics hodder buk.....................plssss share!!!111
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    aqa phys 5 turning points question if any of you can help
    for special relativity questions involving time dilation, length contraction and the mass energy equivalence, is the t0 or l0 the view of the observer or the actual particle?
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    (Original post by babuchang)
    Hey, this should help for the relativity stuff...
    Do you have more notes?
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    Looking for as many questions as possible for Astrophysics.. anyone help with that??
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    (Original post by Smithy-92)
    Looking for as many questions as possible for Astrophysics.. anyone help with that??
    http://cid-5432f573d3fc3f5a.office.l...hysics%20Q.doc

    http://cid-5432f573d3fc3f5a.office.l...hysics%20A.doc

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    heyy
    can anyone post some particle physics notes
    i NEED em =)
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    Thank you!

    Where did you get these from?
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    (Original post by soutioirsim)
    Thank you!

    Where did you get these from?
    Welcome. I had them saved in my favs. last year and completely forgot about it and across it just today!
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    Thanks very much! I assume since you just came across them again, you don't remember where they're from/what spec they belong to/etc?
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    (Original post by Smithy-92)
    Thanks very much! I assume since you just came across them again, you don't remember where they're from/what spec they belong to/etc?
    Welcome. Edexcel- Old syllabus.
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    Questions?
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    (Original post by Smithy-92)
    Looking for as many questions as possible for Astrophysics.. anyone help with that??
    Check these too.

    http://www.khanacademy.org/#cosmology-and-astronomy
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    You know the equation

    Q = Qoe^-t/RC

    and that time constant = RC

    This is a stupid question maybe, but doesnt that mean that -t/RC in the first equation = 1?

    Or is the t in the original equation the time that has passed by? Or something different
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    (Original post by RSM93)
    You know the equation

    Q = Qoe^-t/RC

    and that time constant = RC

    This is a stupid question maybe, but doesnt that mean that mean -t/RC in the first equation = 1?

    Or is the t in the original equation the time that has passed by? Or something different
    RC is the time constant, as you said. The amount of charge left, in the capacitor, is 0.367 (e^-1) it's original value (at t= 0) So yes, -t/RC = 1
    Once t = RC the amount of charge fall by 36.7% of the orginal value.
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    (Original post by Summerdays)
    RC is the time constant, as you said. The amount of charge left, in the capacitor, is 0.367 (e^-1) it's original value (at t= 0) So yes, -t/RC = 1
    Once t = RC the amount of charge fall by 36.7% of the orginal value.
    Thanks seems simple when you understand it :p:
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    (Original post by Summerdays)
    Do you have more notes?
    Yeah which ones do you want? Astro, medical?
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    (Original post by babuchang)
    Yeah which ones do you want? Astro, medical?
    Do you have astro and the mandatory AQA unit 5 topic?

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