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Homework Help: Finding velocity given change in potential

  1. Nov 19, 2008 #1
    1. The problem statement, all variables and given/known data

    An electron is accelerated from rest by a potential difference of 422 V. What is its velocity?

    2. Relevant equations

    KE = .5mv^2

    3. The attempt at a solution

    Since the electron started from rest, there is no KE at the start, just potential. After it is accelerated I assumed that there was not potential and that the electron only had potential energy.
    Doing this, i was able to set up a conservation of energy equation where:
    422 = .5mv^2

    is this the correct way of going about solving this?
  2. jcsd
  3. Nov 19, 2008 #2


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    Your thinking is correct, but you should watch the units carefully. More to the point, what are the energy units that go with 422?
  4. Nov 19, 2008 #3
    eV goes with 422, but KE would be in joules... uh oh! i did some digging and ended up finding that getting the deltaU = q * deltaV (U is change in potential energy, V is change in the potential, q is charge). i multiplied my potential by the charge and then set up the new equation: 6.752E-17 = .5mv^2 and got the right answer. Thanks mate.
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