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Electric potential and conservations of energy

  1. Jan 28, 2012 #1
    1. The problem statement, all variables and given/known data

    For the following image V1=67.9 V, V2=52.8 V, and V3=37.7 V. A proton's speed as it passes point A is 47566.0 m/s and it follows the trajectory shown. What is the proton's speed at point B?

    http://capa.physics.mcmaster.ca/figures/kn/Graph29/kn-pic2944.png [Broken]

    2. Relevant equations

    3. The attempt at a solution

    2.ΔU= 0.5mV2^2-0.5mV1^2

    i then solved for V2 and i didn't get the answer.... can someone elaborate?
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Jan 28, 2012 #2
    Kk i got the answer only because i dropped the negative when i found the potential difference. can someone explain why?
  4. Jan 28, 2012 #3
    ΔU = -q∫[itex]\bar{E}[/itex][itex]\cdot[/itex]d[itex]\bar{r}[/itex]

    Hope that helps.

    You're going to have to be more specific as to what you did. I can't see your calculations, but it probably was a sign error.

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