1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook