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Homework Help: Carbon-14 Activity Problem(s)

  1. Jun 13, 2013 #1
    1. The problem statement, all variables and given/known data

    1) What would you expect the Carbon-14 activity (in counts/minute) to be for a 1.0g sample of Carbon from a 4000-year-old Bristle pine cone?

    2) What would you expect the Carbon-14 in counts/minute to be for a 20g sample of carbon from a 10000 year old fireplace found in a cave in Europe?

    2. Relevant equations

    No idea.

    3. The attempt at a solution

    For both questions I'm assuming I have to find Carbon-14's counts/min rate and then multiply it by 1.0g and 4000yrs to get my answer? My teacher assigned these without any equations which explains why I have none posted above. Can someone please help me get started on this question?
  2. jcsd
  3. Jun 13, 2013 #2


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    If you multiply a frequency per unit mass (count/time-mass) by a mass you will get a frequency. If you then multiply it by a time period what will you get? What are the dimensions of the answer you're after?
    To answer this question you have to understand why C14 levels in living cells are different from those of long dead ones. Try googling C14 dating.
  4. Jun 14, 2013 #3
    When looking up C14 dating, pay attention to the half life of C14, and look for an exponential decaying function something like A = p(1/2)^(t/hl) . I'll leave it to you to figure out what the variables are.
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