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Homework Help: Mass & Energy

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

    If an electron and proton (both initially at rest and
    far apart) come together to form a hydrogen atom,
    13.6 eV of energy is released (mostly as light). By
    how much does the mass of an H atom differ from the
    sum of the electron and proton masses? What is the
    fractional difference ΔM / (m_e + m_p) ?

    2. Relevant equations
    E= √( (pc)^2 + (mc^()2)^2 )

    E of photon= 13.6 eV
    3. The attempt at a solution

    Any help on how to proceed?
    Can I say that energies of rest masses of proton and electron - 13.6 eV = Energy in H?

  2. jcsd
  3. Jul 1, 2013 #2
    You can assume p=0. Then find the change in total energy!
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