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B Free Proton verses Nucleus Proton rest mass

  1. Dec 11, 2016 #1


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    The energy associated with the mass of a free proton in the center of momentum frame where the proton’s momentum is zero is 938.272 (with more decimals).

    What is the rest energy of a single proton inside a Uranium atom? (It could be any other radioactive or fissionable element but I took something common for an example). That is, if I subtracted out the binding energy and all other forms of energy for the proton while inside the atom, how much energy would be left that would only be associated with the rest mass of the proton while it is inside the nucleus?

    I know there are calculations where the total mass of the nucleus is less than the mass of its individual nucleons if the masses of the individual nucleons were summed together. This missing energy goes into forming the binding energy of the atom. But these calculations deal with all the nucleons as a system, whether separated into individual particles or all together in the nucleus. I want to compare the energy associated with the p = 0 rest mass of a separated single proton to the p = 0 rest mass of a single proton in the nucleus.
  2. jcsd
  3. Dec 11, 2016 #2
    It should be the same unless the bound proton transforms into a neutron through β+ decay.
  4. Dec 11, 2016 #3


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    "Rest energy inside a proton" is a problematic concept because a proton inside a nucleus is not "at rest" (without kinetic energy) in any frame. The mass is the same inside a nucleus.
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