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Homework Help: Speed of two charged, insulated spheres?

  1. Oct 2, 2012 #1
    1. The problem statement, all variables and given/known data

    Two insulating spheres have radii 0.300 cm and 0.500 cm, masses 0.450 kg and 0.700 kg, and uniformly distributed charges of -2.00 µC and 3.00 µC. They are released from rest when their centers are separated by 1.00 m.
    (a) How fast will each be moving when they collide? (Hint: Consider conservation of energy and of linear momentum.)

    2. Relevant equations
    F = keq1q2/r2
    v = at + v0
    Δs = v0t + .5at2


    3. The attempt at a solution

    I found the electrostatic force on the objects. Since they have opposite charges, I know that they move towards each other. I found their accelerations by dividing by their respective masses, and then plugged those into some of the kinematics equations to find the final velocity.

    I can see that my methods/assumptions are wrong, I'm just not exactly sure about how to go about this problem.
     
  2. jcsd
  3. Oct 2, 2012 #2
    Acceleration isn't constant as force increases while spheres get closer
     
  4. Oct 2, 2012 #3
    Yes, but then how do I solve it?
     
  5. Oct 3, 2012 #4
    Your hint says you should use the law of conservation energy and momentum.
     
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