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stupid phy6 question, calculation question help. watch

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    January 2003 - phy6
    question
    2 (iii) Calculate the kinetic energy of the pair of α -particles in joules,

    there some data like mass of li, proton and alpha particle. The paper is on the taggart site.
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    http://www.sgcscience.co.uk/physics/...uary2003MS.doc
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    Do you have a link to the question?
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    I just did that yesturday.
    First find the mass defect from e=mc^2.
    This is from the nuclear equation.

    Mass before = 8.02165kg
    Mass after = 8.003kg
    mass defect = 0.01865kg


    I then got it all wrong!
    I dont understand why they times by the mass of an electron?
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    (Original post by SinghFello)

    Mass before = 8.02165kg
    Mass after = 8.003kg
    mass defect = 0.01865kg


    I then got it all wrong!
    I dont understand why they times by the mass of an electron?
    Well, I think the unit is u not kg
    And they times mass of 1 u, not mass of 1 e
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    i did this in particle physics, you have to find the difference in u then convert to kilograms [this is where particle physics is good]

    but how the *** did they get that difference in mass?

    i thought it would be either
    proton + li - [2 alphas]
    or
    proton - [2 alphas]

    i dunno how they did it :mad:
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    ah i done it!

    i got alpha mass n proton mass mixed up lol

    so you do this
    mass before = li + proton [in u]
    mass after = 2 x alhpa mass

    e=mc^2
    as e = joules
    mass needs to be in kgs, so convert with 1.66 x10^-27kg = 1u

    phew
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    (Original post by nas7232)
    how did you get Mass after = 8.003kg
    He just times 2 mass of alpha particle
    m = 2 * 4.00150 u = 8.003u
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    (Original post by nas7232)
    i did this in particle physics, you have to find the difference in u then convert to kilograms [this is where particle physics is good]

    but how the *** did they get that difference in mass?

    i thought it would be either
    proton + li - [2 alphas]
    or
    proton - [2 alphas]

    i dunno how they did it :mad:
    That's how they did do it:
    (H + Li) - 2He
 
 
 
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