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Homework Help: Electric Fields and Kinetic Energy of protons

  1. Apr 11, 2010 #1
    1. The problem statement, all variables and given/known data

    Each of the protons in a particle beam has a kinetic energy of 3.25 x 10^-15 J. What are the magnitude and direction of the electric field that will stop these protons in a distance of 1.25 m?

    2. Relevant equations

    Felectric = kC (q*q/r^2)
    Electric Field= Felectric/q
    Electric Field= kC (q/r^2)
    Velocityfinal= velocityInitial + a*t
    Velocityfinal^2 = VelocityInitial^2 + 2a(d)

    3. The attempt at a solution

    I need help with this.
  2. jcsd
  3. Apr 11, 2010 #2


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    Homework Helper

    Work done by the electric force = change in the KE.
    Initial KE is given. Final KE = .........?
    Work done by the electric force F = ......?
    And as you have stated E = f/q.
    Now try.
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