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Homework Help: Separation and Potential/Kinetic Energy

  1. Feb 26, 2009 #1
    1. The problem statement, all variables and given/known data
    Two protons that are very far apart are hurled straight at each other, each with an initial kinetic energy of 0.19 MeV, where 1 mega electron volt is equal to 1106 (1.610-19) joules. What is the separation of the protons from each other when they momentarily come to a stop?

    2. Relevant equations
    Total energy = kinetic energy + potential energy
    (1/4 pi e0)*(q1q2/r)

    3. The attempt at a solution
    So since the initial distance is very far away, we can assume that potential energy is so close to zero that it can be neglected. Therefore, due to the law of conservation of energy, when the kinetic energy is 0, the potential energy will be 0.19 MeV, or 3.044135274e-14 J. I tried setting this equal to the equation (1/4 pi e0)*(q1q2/r) and solving for r, but my answer is incorrect. Can somebody tell me what I'm doing wrong?
    Thanks in advance!
  2. jcsd
  3. Feb 26, 2009 #2


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    Science Advisor
    Homework Helper

    If this where the Physics Psychics Forum, somebody might be able to tell you what you did wrong. Why don't you tell us what you got and what numbers you put in? There is nothing wrong with your approach.
  4. Feb 26, 2009 #3
    Its okay I ended up getting it right. I simply did not multiply the 0.19 MeV by 2
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