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Hw problems

  1. Feb 21, 2006 #1
    How fast will the electron be travelling?

    Ek = ½ MV^2
    V = 2Ek/M
    V = √2Ek/M
    = √ 2 x 1.6x10^-19/9.1 x 10^-31
    = ???
    This number is too high since it implies that a larger voltage (say 10) would make the electron travel faster than light. The reason is?????
  2. jcsd
  3. Feb 21, 2006 #2


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    You might want to give at least SOME info about the problem and what you're trying to do.
    Were you solving E=1/2mv^2 for v?

    By the way. You're using the classical formula 1/2mv^2 for the kinetic energy. Ofcourse you can get velocities faster than light if you don't take relativity into account.
  4. Feb 21, 2006 #3
    That's right. When doing with high speed, you have to apply the relative theory.
  5. Feb 21, 2006 #4
    That doesn't mean your answer might not be correct. I've found that kind of mistake in any number of Introductory level texts. Check with your instructor.

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