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Quick Question on AS Physics Unit 1 Paper Watch

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    Hi, I was wondering if anyone can give me some info about a question on AQA Physics A Specimen Paper(Unit 1).
    The question is:
    Determine the specific charge of a nucleus of Cs 133(Atomic relative Mass)/55(Proton Number).

    So here's what I did.

    Specific Charge = Charge / Mass
    The electronic charge unit (e) = 1.6 X 10^-19 C
    So 55 X e = 8.8 x 10 ^-18 (Which is the charge)
    And 133 X Proton mass = 2.2211 X 10 ^-25 (The Mass)

    So the out come should be 3962000.81 = 3.962 X 10^7 C Kg-1

    My confusion is the AQA Mark scheme says this
    specific charge (= charge/mass) = 55 × 1.6 × 10^-19/137 × 1.67 × 10^-27
    AQA Answer = 3.85 × 10^7 C kg-1
    My Answer = 3.962 X 10^7 C Kg-1

    Where Am I wrong? Also I do not understand where AQA have got 137 as the relative mass number for Cs on the periodic table says 133?

    Any Help?
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    Anyone?
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    Perhaps they have used separate values of mass for neutrons and protons? That's all I can think of. The answer is so close it shouldn't be anything else...plus I just got the same as you.

    Try calculating the masses off protons + neutrons and you should get the right answer.
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    ...Naaaah, didn't work, did it?
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    Oops, didn't read your post properly :P Definitely something to do with that 137/133 thing. It definitely says 133 in the question then goes on to use 137?
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    It looks like an error in the mark scheme to me, for some reason they're using Caesium-137, when the question paper clearly states Caesium-133. I've found that the AQA specimen papers quite often have mistakes in their mark schemes, presumably because they're not checked as rigorously as the real papers.
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    Thanks. I am quite confused on this equation.

    From these energies in joules, we can work out the speeds at which the electrons travel using v2 = 2 Ek/m. Mass of an electron = 9.11 × 10-31 kg.
    so 100eV equals v = 5.92 × 105 m/s
    According to t he mark scheme.
    Yet every time i try it. I get a completely different answer.
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    (Original post by westarmy)
    Thanks. I am quite confused on this equation.

    From these energies in joules, we can work out the speeds at which the electrons travel using v2 = 2 Ek/m. Mass of an electron = 9.11 × 10-31 kg.
    so 100eV equals v = 5.92 × 105 m/s
    According to t he mark scheme.
    Yet every time i try it. I get a completely different answer.
    Hi, I was wonderin' do you have an electronic version of this paper? (AQ & MS). If so could you please upload? ...
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    Hey,
    Forces acting on a vertically ascending balloon: Drag, Upthrust and Weight.
    Will Drag be upwards or downwards?
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    (Original post by westarmy)
    Thanks. I am quite confused on this equation.

    From these energies in joules, we can work out the speeds at which the electrons travel using v2 = 2 Ek/m. Mass of an electron = 9.11 × 10-31 kg.
    so 100eV equals v = 5.92 × 105 m/s
    According to t he mark scheme.
    Yet every time i try it. I get a completely different answer.
    I dunno what the poster above is talking about, but ill help, youve made a very simple but common mistake Ek or work is measured in Joules. you need to convert the 100eV to joules.

    Multiply 100ev by the charge of one electron (1.6x10^-19) and you will get the Ek

    Then put that into the equation and rember to square route the equation.

    I got an answer of 5.926x10^6 ms-1
 
 
 
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