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Homework Help: Proton decay

  1. Dec 2, 2009 #1
    1. The problem statement, all variables and given/known data

    Grand unification theories predict that the proton has a long but finite lifetime. Current experiments based on detecting the decay of protons in water infer that this lifetime is at least 10^32 years. Assume 10^32 years is, in fact, the mean lifetime of the proton. Estimate the expected time between proton decays that occur in the water of a filled Olympic-size swimming pool. An Olympic-size swimming pool is 100m x 25m x 2.0m.

    2. Relevant equations

    not sure

    3. The attempt at a solution

    I am not really sure what the question is asking. Clearly the volume of the pool matters, otherwise it probably wouldn't be given, but I don't know where to start. Can anybody offer an explanation as to where I should start. Any help would be much appreciated.
  2. jcsd
  3. Dec 2, 2009 #2


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    Science Advisor
    Gold Member

    The volume of the water will tell you how much water there is (M=pV, and you know the density of water), from there you can tell how many molecules of water there are and therefore how many protons there are. Then you can tell how many protons decay per second using basic radioactive decay laws.
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