# Need help with Phys 2 problem

1. Oct 16, 2006

### mustangguy289

Ive got this one homework problem that i am totally clueless on. Any help?
"Two insulating spheres having radii 0.34 cm and 0.54 cm, masses 0.13kg and 0.58 kg, and charges -3x10^-6 C and 2x10^-6 C are released from rest when their centers are seperated by 1.2m.

How fast is the smaller sphere moving when they collide? Answer in units m/s."

2. Oct 16, 2006

### mustangguy289

Anyone know how to do this. Our professor hasnt really showed us yet.

3. Oct 16, 2006

### OlderDan

This problem has to do with electrical potential energy and conservation of energy. It is very similar to a gravitational attraction problem, but here the force is electrical instead of gravitational.

4. Jan 2, 2007

### lizzyb

wrong forum

Last edited: Jan 2, 2007
5. Jan 4, 2007

### tim_lou

use conservation of energy.

what is the initial potential energy? what is the final potential energy?

by gauss's law the electric field of uniformly charged spheres can be treated in the same manner as point charges (when distance is greater than the radius). So from there, you should be able to find the potential energy.