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Homework Help: Speed of electron

  1. Jan 27, 2010 #1
    1. The problem statement, all variables and given/known data

    Two electrons separated by 2*10^(-10)m are released from rest. What is the speed of each electron when they are a large distance apart. (Both electrons will have the same speed.) The answer should be 1.13*10^(6)m/s.

    2. Relevant equations


    3. The attempt at a solution

    I am not sure what formula to use. If I were given kinetic energy I think I could figure this one out, but can't with the info given. Any help on where to start?
  2. jcsd
  3. Jan 27, 2010 #2
    The relevant equations are the equations for electrical potential energy and kinetic energy.
    At a large distance apart, all of the potential energy stored at the start (when the e- are separated by 2*10^(-10) m) have been converted to kinetic energy.
  4. Jan 27, 2010 #3
    Some large distance probably refers to infinite. Find the initial energy of the system, which would be the electric potential energy, U. At infinite, U would mostly convert to kinetic energy, K.

    If your answer exceeds the speed of light (or comes considerably close), you might want to add relativistic adjustments.
  5. Jan 27, 2010 #4
    Yes. I had forgotten to mention relativistic adjustments as well. Also keep in mind that the electron has an elementary charge (this will be useful when determining the electric potential energy.)
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