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Homework Help: Work electron problem

  1. Oct 18, 2004 #1
    How much work is required to stop an electron (m = 9.11×10-31 kg) which is moving with a speed of 1.86×106 m/s?

    Ef-Ei=W
    Kenetic E - Potential E = Work
    I don't think there is any potential energy in this case...

    I'm a bit stuck. Any suggestions?
     
  2. jcsd
  3. Oct 18, 2004 #2

    Doc Al

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    Staff: Mentor

    Keep going. [itex]W = \Delta {KE}[/itex], so what's the kinetic energy of that electron?
     
  4. Oct 18, 2004 #3
    is the change in kenetic energy 1/2mv^2?
     
  5. Oct 18, 2004 #4

    Doc Al

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    Staff: Mentor

    The initial KE of the electron is 1/2mv^2; the final is zero. So, yes, the change in KE is (minus) 1/2mv^2.
     
  6. Oct 18, 2004 #5
    Great thank you that was a whole lot easier than I made it out to be!
     
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