# physics

A sample of charcoal from an archaeological site contains 55 g of carbon and decays at a rate of .877 Bq. How old is it?

ok I am totally lost, I don't know where to start

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asked by J
1. The half life of C=14 is 5730 years.
A living organism has a decay rate of 15.2 decays per minute per gram.
You have a 55 gram sample; therefore,
55 g x 15.2 d/min*g = 836 d/min for the 55 g sample. That's the initial rate or Ro.

ln(Ro/R) = kt
So Ro is the intial rate from above.
R = 1 Bq = 1 decay/sec x 60sec/min = 60 decays/min. This is today's rate for the 55 g carbon.
k is a constant to be determined. How to get the constant is below.
t is the unknown. Solve for that.
k = 0.693/half-life = 0.693/5730 = ??
Post your work if you get stuck.

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posted by DrBob222

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