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OCR Physics B - Rise and fall of the clockwork universe - 28th Jan watch

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    Did anyone else use the equation pv=nrt for the piston question and find R and avogardros constant from the formula book?
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    (Original post by Katie_08)
    Did anyone else use the equation pv=nrt for the piston question and find R and avogardros constant from the formula book?
    I used pV = NkT rather than that, although if you did what you said correctly it should have worked.

    EDIT: Actually if I remember correctly that was a "Show" question, so you'll know if it worked. Silly me. I'm going to stop thinking about exams now, they're over for January. Time to relax and wait for results! Good luck everyone.
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    Didn't it give you the value for K? And surely that's a good enough hint to use that equation?
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    That went really bad...
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    (Original post by Skadoosh)
    Didn't it give you the value for K? And surely that's a good enough hint to use that equation?
    Yer but i didnt even though that equation exsisted my whole physics class was convinced that it was a mistake on the question paper and that they had meant to give us R instead.
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    (Original post by bluespacetiger)
    I used pV = NkT rather than that, although if you did what you said correctly it should have worked.

    EDIT: Actually if I remember correctly that was a "Show" question, so you'll know if it worked. Silly me. I'm going to stop thinking about exams now, they're over for January. Time to relax and wait for results! Good luck everyone.
    O dear i forget it was a show that question so i dont even know if i got the answer right not, stupid me.
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    (Original post by Katie_08)
    Yer but i didnt even though that equation exsisted my whole physics class was convinced that it was a mistake on the question paper and that they had meant to give us R instead.
    Hmmmmm. As I recall, and I'm not 100% on this, the question asked you to find the number of molecules, as opposed to the number of moles.

    Therefore, you have to use the equation pV=NkT as N=number of molecules.
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    (Original post by Skadoosh)
    Hmmmmm. As I recall, and I'm not 100% on this, the question asked you to find the number of molecules, as opposed to the number of moles.

    Therefore, you have to use the equation pV=NkT as N=number of molecules.
    Doesnt make a difference if she then multiplied answer by 6.02x10^23!
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    you could use the other equation and use the Av constant for number of particles in a mole, if you were feeling particularly bad at physics today like me.
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    (Original post by LearningMath)
    Doesnt make a difference if she then multiplied answer by 6.02x10^23!
    Yes, you're right. Nevermind.
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    :no: It went bad. Astronaut-and-his-rocket question sucked. And some others too... Guess I might have to do a retake..
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    Interesting paper. A lot more interesting applications of the syllabus. The copper question was a bit strange and the electron emission was interesting. I agree that section A was tougher than usual. I know I dropped 5 marks minimum from not answering stuff (melting point of copper and why the internal energy decreases in the piston), or getting stuff wrong (Calculated the time dilation the wrong way round).

    Overall, I think I did alright on the rest of the paper, so hopefully the grade boundaries work in my favour.

    edit, who here thinks that radioactivity question was a bit ambiguous? What is the significance of the decay constant? What do you mean significance?
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    OMG

    it was an alright ish paper, there was some wtf questions there
    specially the one at the end abouit wavelength and capacitance
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    any 1 can scan the paper n put solutions up
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    hated that paper so much, defintly retaking
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    (Original post by cryptopian)
    Interesting paper. A lot more interesting applications of the syllabus. The copper question was a bit strange and the electron emission was interesting. I agree that section A was tougher than usual. I know I dropped 5 marks minimum from not answering stuff (melting point of copper and why the internal energy decreases in the piston), or getting stuff wrong (Calculated the time dilation the wrong way round).

    Overall, I think I did alright on the rest of the paper, so hopefully the grade boundaries work in my favour.

    edit, who here thinks that radioactivity question was a bit ambiguous? What is the significance of the decay constant? What do you mean significance?
    Yeah I know what you mean on the last part. I just put the basic definition of the decay constant and it's role in the probability of the decay.

    Like you said, I won't mind low grade boundaries.
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    grr anyway else not realize that k != k in one of the questions, one was stiffness constant and the other boltzman factor
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    i thought that paper was not tooooo bad. I prefer this type of paper more than others because it had some intruiging questions in it. enjoyed it!
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    (Original post by Katie_08)
    I thought this paper was harder than all the past papers we did but i did expect it after last years June exam though. Even the momentum question was quite tricky.
    I didn't like this paper at all :\

    Argh think I messed up bad.
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    (Original post by kylesawhney)
    Hey,

    E = 1/2 k (force per unit displacement) A²

    A= 0.15 x d (found in earlier question)

    E = k (boltzmann) T

    T = E/k (boltzmann)

    Sub in E found earlier and you get the melting point :-)

    I got around 1300K
    where did you get the stiffness constant from?
 
 
 
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