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EDEXCEL A2 Physics EXAM Unit 4 Physics On The Move 20th June 2016 (NOT I-A-L) Watch

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    (Original post by oShahpo)
    r = mv^2 / F sin22 .
    can someone please verify this for this question:


    was the force labeled in the diagram (from friction or whatever was in the question) just the frictional force or the resultant (centripetal force)
    basically what im asking is, is that force in the diagram F= mv^2 / r
    or is the centripetal force the horizontal to that?
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    (Original post by jtebbbs)
    Yeah I always try to in physics
    also did you get 20% for max?
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    Does anyone know if there is an unofficial mark scheme anywhere?
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    One of the questions was about why the silicon plate had such a small capacitance, anyone remember what they answered for that?
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    (Original post by Ilaawef)
    One of the questions was about why the silicon plate had such a small capacitance, anyone remember what they answered for that?
    I said that it was to do with the time constant (RC) needing to be low but I'm not sure if that is correct?
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    (Original post by Ilaawef)
    One of the questions was about why the silicon plate had such a small capacitance, anyone remember what they answered for that?
    small rc so discharges quickly, also holds less charge so more sensitive.
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    (Original post by funkyfig)
    I said that it was to do with the time constant (RC) needing to be low but I'm not sure if that is correct?
    I'm not sure myself, I didn't actually get to answer it because it was confusing. All I remember was the question stating it needs to detect minute changes in the distance. Probably because silicon is used in sensitive circuits?
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    (Original post by oShahpo)
    small rc so discharges quickly, also holds less charge so more sensitive.
    Ah alright, I guess I was somewhere on the right track, I just ran out of time going over questions I skipped.
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    (Original post by lauren con)
    I got 80% too! doesn't seem like many people got the same though
    Me too! Though I wasn't particularly confident about it, it made the most logical sense to me that it would be the way to go about that question.
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    (Original post by ajaxkiller)
    can someone please verify this for this question:


    was the force labeled in the diagram (from friction or whatever was in the question) just the frictional force or the resultant (centripetal force)
    basically what im asking is, is that force in the diagram F= mv^2 / r
    or is the centripetal force the horizontal to that?
    to find r isn't it?

    Fsin22 = mv^2/r
    Fcos22 = mg

    tan22=v^2/rg

    That's what I did anyway??
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    (Original post by kidlikethat)
    to find r isn't it?

    Fsin22 = mv^2/r
    Fcos22 = mg

    tan22=v^2/rg

    That's what I did anyway??
    they gave you the mass of the guy in the question, your method ignores mass, surely if they wanted you to eliminate mass, they wouldnt have given it to you in the first place.....
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    (Original post by ajaxkiller)
    they gave you the mass of the guy in the question, your method ignores mass, surely if they wanted you to eliminate mass, they wouldnt have given it to you in the first place.....
    No, they gave you the mass so that you don't get confused and so that you can follow the straight forward method. Eliminating the mass is acceptable as circular motion never depends on the mass anyway.
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    Im having a bloody fit over here because I keep getting 20.5m for the radius but everyone is getting 20.4m
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    is there any vote on how people found it/grade boundaries?
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    (Original post by student143)
    is there any vote on how people found it/grade boundaries?
    http://www.thestudentroom.co.uk/show....php?t=4176400
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    What do you think the grade boundaries will be ? Also has anyone got an unofficial mark scheme yet ?
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    (Original post by Salty carpet)
    Im having a bloody fit over here because I keep getting 20.5m for the radius but everyone is getting 20.4m
    thats because you are using g as 9.8 and not 9.81
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    (Original post by linaxq)
    thats because you are using g as 9.8 and not 9.81
    Do a-level maths they said, it'll help you with physics they said
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    (Original post by Salty carpet)
    Do a-level maths they said, it'll help you with physics they said
    lmao i did the same thing but i went back a realised.
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    (Original post by Jordan97)
    You had to find the charge difference when the plates were at 3.5mm and 4.2mm, not 2.8mm and 4.2mm
    i agree because it was asking about the maximum charge decrease allowance charge only decreases when the d increases.
 
 
 
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