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Homework Help: What is the Potential difference?

  1. Sep 16, 2007 #1
    1. The problem statement, all variables and given/known data

    As a positron moves through a region of space, its speed decreases from 9.20*10^6 m/s to 2.20*10^6 m/s. The electric force is the only force acting on the positron.

    2. Relevant equations

    KE1 + U1 = KE2 + U2
    Where KE is kinetic energy and U is potential energy.

    3. The attempt at a solution

    Using the above equation I have:

    Potential Difference = [tex]\\text{$\Delta $v} = \frac{1/2m\left(v_f^2-v_i^2\right)}{q}[/tex]

    Where m is the mass of the positron, 9.1E-31 kg, and q is the charge of the positron, 1.6E-19 C. The v's are the final and initial speeds. The potential difference comes out to be: 77 V when I solve it.

    I am not getting the correct answer. Am I proceeding about this the right way?
    Last edited: Sep 16, 2007
  2. jcsd
  3. Sep 16, 2007 #2


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    Homework Helper

    It should be vi^2 - vf^2 in the numerator... but other than that everything looks right. check your calculations... I'm getting a different number.
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