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Homework Help: Work-energy principle

  1. Aug 6, 2009 #1
    1. The problem statement, all variables and given/known data
    2 large metal sheets are seperated by a potential of 40 volts by a vaccum. When the proton particle (mass 1.67x10e-27 kg)is released close to the (+) sheet it moves closer to the (-) sheet by way of electric field. What's the KE right before the proton smacks the other sheet? And what's the velocity of before striking the (-) sheet?

    2. Relevant equations

    KE=>q*v and EK=mv^2/2

    3. The attempt at a solution

    KE= 1.6x10e-19(40)=6.4x10e-18

    v= ?
  2. jcsd
  3. Aug 6, 2009 #2


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    Gold Member

    What's the formula for the kinetic energy of an object (in terms of the object's velocity)?
  4. Aug 6, 2009 #3
    Can anyone help me with this?

    I think the velocity is 87548 m/s. Is this correct?
  5. Aug 6, 2009 #4


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    Homework Helper

    Your answer is correct.
  6. Aug 6, 2009 #5
    what about the first part for KE?
  7. Aug 7, 2009 #6


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    Homework Helper

    If that isn't correct, you wouldn't have gotten the right answer for v. So yes, KE=qV, and your calculation is right as well.
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