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Homework Help: Speed of electron when kinetic energy given

  1. Nov 23, 2005 #1
    Hey guys, my teacher saked us to solve for the speed of an electron when the kinetic energy is 6.7*10^-19 Joules

    So, I fit in the mass of an electron, and the kinetic energy, and solve for v in the 1/2mv^2 equation??

    Thanks a lot
  2. jcsd
  3. Nov 23, 2005 #2
    well obviously yes...thats one way of doing it!
  4. Nov 23, 2005 #3


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    Staff: Mentor

    For that energy, the classical kinetic energy equation will work fine. If the energy were 100 times larger, you'd probably need to use the relativistic kinetic energy equation, unless your answer didn't have to be very accurate. If the energy were 1000 times larger, you'd definitely need the relativistic equation.
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