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Homework Help: Finding potential difference to accelerate the ion

  1. Mar 7, 2009 #1
    1. The problem statement, all variables and given/known data
    What potential difference is needed to accelerate a He + ion (charge +e, mass 4 u) from rest to a speed of 2.0 * 10^6 m/s?


    2. Relevant equations
    Kf + Uf = Ki + Ui
    U = qV where V is potential difference (volts)

    K = (1/2)mv^2

    3. The attempt at a solution
    I chose the rest point to be r = 0, so even with U = Kq_1q_2/r, it would equal zero at the start.
    Then:
    (1/2)mv^2 = -qV

    V = (-1/2q)mv^2
    = -(2q/)uv^2
    m = u* 1.66*10^-27 kg/u = 1.66*10^-27 kg

    V = -(2/(1.6*10^-19 Coulombs)) * (1.66*10^-27 kg)(2.0*10^6 m/s)^2
    = -83000 volts

    Is this right?
     
    Last edited: Mar 7, 2009
  2. jcsd
  3. Mar 7, 2009 #2
    Correct.
     
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