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Homework Help: Nuclear decay of banana

  1. Apr 6, 2014 #1
    1. The problem statement, all variables and given/known data

    If all of the energy from decay of the 40-K in one banana could be captured and converted into electrical energy, how many bananas would be needed to power a 100 W light bulb?

    There is 358 mg potassium-K per 100 grams of banana

    half life of potassium-40 is 1.248(3)×109 y

    2. Relevant equations

    k= (0.693/half-life)

    3. The attempt at a solution

    If a banana weighs 125 grams on average then there is 447.5 grams of potassium-40 in one banana.

    (358)(1.25) = 447.5g
    - - - - - - - - - - - - - -
    k=(0.693/1.248(3)×10^9 y) = 5.55×10^-10

    k = 5.55×10^-10
    Ao = 447.5 g
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Apr 6, 2014 #2


    User Avatar

    Staff: Mentor

    That's 447.5 mg of K-40

    You'll need an equation that includes the energy of decay of the isotope.
    Last edited: Apr 6, 2014
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