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Homework Help: Need help with a question about momentum

  1. Apr 21, 2009 #1
    1. The problem statement, all variables and given/known data

    How fast would a proton have to travel to have the same momentum as a 6.0-MeV photon

    2. Relevant equations
    P= E / C

    3. The attempt at a solution
    P= E / C
    = 6.0-MeV / 3.00x108m/s
  2. jcsd
  3. Apr 21, 2009 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Welcome to Physics Forums.

    You need to be careful with your units here, your mixing natural units and S.I. units. You need to pick a system and stick to it.
  4. Apr 21, 2009 #3

    What's the problem here? Have you even put in any thought to it?

    Yes P = E/c but if you're going to use that you need to make sure your E and c are in SI - that is - m/s and J

    Once you find that you can equate that with the momentum of a proton - mv. You can look up the mass of the proton, and solve for v
  5. Apr 21, 2009 #4
    That was my problem, I hadn't realized that i had the different units. Thank you!
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