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How to find the age of boat (carbon dating)? please

  1. Jan 28, 2015 #1
    1. The problem statement, all variables and given/known data
    The carbon in living matter contains fixed proportion of the radioactive isotope carbon-14. The carbon-14 in 1.00g of living matter has an activity of 0.250Bq. The half life of carbon-14 is 5730 years.
    (a) Calculate (i) The decay constant in s-1 (ii) the number of carbon-14 atoms required to produce an activity of 0.250Bq.
    (b) When a plant dies the proportion of carbon-14 decreases due to radioactive decay. A 1.00g sample of carbon from an ancient boat has an activity of 0.0625Bq. Determine the age of the boat.

    2. Relevant equations
    A = yN
    A = A0e-yt
    A0 = yN0
    A = A0e-yt
    3. The attempt at a solution
    I've worked out (a) (i) to be 2.48x10-12 and (ii) N = 1.01x1011

    I don't know how to work out (iii) because I don't know how to work out N0 or A0. I found using A = yN --> N = A/y = 2.52x1010

    How to find either A0 or N0 so that I can use A = A0e-yt or N = N = N0e-yt?
  2. jcsd
  3. Jan 28, 2015 #2

    Simon Bridge

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    Science Advisor
    Homework Helper

    You do it using proportions.

    What fraction of the sample was C14 when it was new?
    What fraction is it now?
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