Ratio kinetic energy of alpha particle / kinetic energy of proton

  1. 1. The problem statement, all variables and given/known data
    A photon and alpha particle are accelerated from rest through the same potential difference.
    After acceleration what is the ratio kinetic energy of alpha particle / kinetic energy of proton?

    2. Relevant equations
    I guess I have to use eV = 1/2mv^2

    3. The attempt at a solution
    I dont know what value have to be used in place of e in equation eV = 1/2mv^2
    the mass of alpha particle is approximately 4 times of photon and that's all i know
    I guessed the answer as 4 but the answer was 2
    I think there is something to do with the velocity of alpha particle and photon but i'm stucked can not think of anything..
  2. jcsd
  3. An alfa particle has two protons, so that's twice the charge of one proton.
  4. Thanks a lot! So i didnt have to know the exact charges but the ratio
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