# Speed of two charged, insulated spheres?

1. Oct 2, 2012

### XianForce

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.

2. Oct 2, 2012

### szynkasz

Acceleration isn't constant as force increases while spheres get closer

3. Oct 2, 2012

### XianForce

Yes, but then how do I solve it?

4. Oct 3, 2012

### szynkasz

Your hint says you should use the law of conservation energy and momentum.