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19/05/10 Edexcel Phy 6(6PH08) watch

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    ah hopefully they will accept my version of the K.E %...HAHA
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    Hey guys,
    Well for K.E. i did something sooo stupid.. i disregarded the lowest time value (2.76s i think) saying it is anomalous. Ugh i feel so stupid, and i'm just wondering how many marks i'll get if i did the rest of the question right? I got 35% for the percentage uncertainty of K.E., which sounds about right if you compare with people who didn't disregard one of the values.
    For Q4, for the question about outlining a simple experiment to identify a gamma source, i said vary the distance between the source and detector to greater than 10m, and if the Count rate is still significantly higher than the background count rate, then the source emits gamma rays. Is that what you guys got?
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    (Original post by taimoorsohail)
    Hey guys,
    Well for K.E. i did something sooo stupid.. i disregarded the lowest time value (2.76s i think) saying it is anomalous. Ugh i feel so stupid, and i'm just wondering how many marks i'll get if i did the rest of the question right? I got 35% for the percentage uncertainty of K.E., which sounds about right if you compare with people who didn't disregard one of the values.
    For Q4, for the question about outlining a simple experiment to identify a gamma source, i said vary the distance between the source and detector to greater than 10m, and if the Count rate is still significantly higher than the background count rate, then the source emits gamma rays. Is that what you guys got?
    I said:

    -Measure average background count
    -Measure count rate of source with a 3mm aluminium sheet between the source and the detector
    -If count rate is still significantly higher than background, the source emits gamma radiation.

    I think both our answers should be correct?
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    (Original post by Xtian)
    I said:

    -Measure average background count
    -Measure count rate of source with a 3mm aluminium sheet between the source and the detector
    -If count rate is still significantly higher than background, the source emits gamma radiation.

    I think both our answers should be correct?
    hmmm.. yeah i was going to put that but then i saw it says ' you have a detector and a source'. The question didn't say anything about an absorber or any other material. Which is why i decided to use air as my 'absorber'....
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    (Original post by taimoorsohail)
    hmmm.. yeah i was going to put that but then i saw it says ' you have a detector and a source'. The question didn't say anything about an absorber or any other material. Which is why i decided to use air as my 'absorber'....
    Tbh I think your answer makes sense (although I went with the absorber material thing). I think the distances travelled by each type of radiation is quoted somewhere in our text book, no? Is that where you got your 10m from?
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    I guess you CAN you air as your absorber as beta and alpha cannot penetrate several cm of air.

    But I just used 3mm cause I say this sort of question in a past paper and 3mm was used in the method. [they didn't ask us to describe the method they provided one]
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    I got 0.046 for mm^-1 but I didn't round off to 0.05.

    Also, am I the only one who look this outrageously high hubble gradient? I got 69.1 T_T I guess my best fit wasn't so best fit.
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    (Original post by fredbraty)
    P.S:You cant do any calculations with absolute uncertainties.For example if u=2h/t
    you are not allowed to find the absolute uncertainty of h and then add it to the absolute uncertainty of t because they are two completely different physical quantities.The absolute uncertainty of h is in mm and the absolute unertainty of t is in seconds.You cant add 1mm+0.26s and say that the unertainty of u is 1.26.
    This is only allowed in % uncertainties because they are all percentages.
    Yeah makes sense. I still don't think that quadrupling the KE %uncertainty is right though..
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    (Original post by dancing.barefoot)
    Yeah makes sense. I still don't think that quadrupling the KE %uncertainty is right though..
    well that moment i thought:They have the same velocity so the uncertainty in calculating the K.e is "one".But then,we have too bodies moving so the uncertainty should be more than if there was only one.And i chose the bigger one.Ah well we will see
 
 
 

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