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Homework Help: Particle kinetic energy

  1. Jul 18, 2010 #1
    1. The problem statement, all variables and given/known data

    A particle with charge -3e is accelerated from rest through a potential difference of 200v .
    This gives the particle a kinetic energy of????
    2. Relevant equations



    3. The attempt at a solution
    what does a charge of -3e mean???(-3*2.71...???) to kind the KE wouldn't i need a mass too??
     
  2. jcsd
  3. Jul 18, 2010 #2
    e = charge of an electron.
    Try using conservation of energy?
     
  4. Jul 18, 2010 #3
    ok so the P.d = Ke??
    I cant see that - can you give me a bit more please.
     
  5. Jul 18, 2010 #4
    when a charged particle passes through a PotDif it "gains energy." (from the fields) since this is a particle of (assumed) no internal structure, the energy it gains will be in kinetic, not potential. Therefore you dont need a mass, the question just wants the energy.

    the equation you need is indeed E = q.V (where q is the charge on the particle)

    to better understand this, remember that we assume the particle does not "see" the potential when it is at an infinite distance from it (potential **difference** from that at infinity).
    So in essence, the value of KinEn is how much the potential "wants" the particle to pass through it.
     
    Last edited: Jul 18, 2010
  6. Jul 18, 2010 #5
    thanks Onamor - problem solved
     
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