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Homework Help: Kinetic Energy of Charged Particle

  1. Feb 20, 2008 #1
    [SOLVED] Kinetic Energy of Charged Particle

    1. The problem statement, all variables and given/known data
    Particles A (of mass m and charge Q) and B (of m and charge 5Q) are released from rest with the distance between them equal to 0.9976 m. If Q=33e-6 C, what is the kinetic energy of particle B at the instant when the particles are 2.9976 m apart?


    2. Relevant equations
    U=kq1q2/r
    K=(mv^2)/2
    ΔU+ΔK=0
    F=ma

    3. The attempt at a solution
    I solved for the potential energy at both distances using U=kq1q2/r to find Ui=49.0683 J and Uf=16.3299 J. Then I used conservation of energy to find K so K=Ui-Uf and got K to be 32.7384 J. But I'm not sure how to get just the kinetic energy of particle B. I tried to sum the forces and use Newton's third law to find acceleration to see if that would help but I don't know how to find it without knowing the mass. I'm not sure if maybe I have to do a ratio to find the energy? I don't know what to do.
     
  2. jcsd
  3. Feb 20, 2008 #2
    nevermind, i figured out its just half of the system kinetic energy
     
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