# Electricity Questions

1. Jul 4, 2006

### StudentofPhysics

Two particles each have a mass of 5.3 10-3 kg. One has a charge of +5.0 10-6 C, and the other has a charge of -5.0 10-6 C. They are initially held at rest at a distance of 0.75 m apart. Both are then released and accelerate toward each other. How fast is each particle moving when the separation between them is one-half its initial value?

ok, I know:
q1 = +5.0 x 10^-6 C
q2 = -5.0 x 10^-6 C
r = 0.75m
m = 5.3 x 10^-3 kg

Since they are opposite charges they will atract eachother.

I can't seem to figure out where to begin on what formula to use to discover the speed without any time.

2. Jul 4, 2006

### fargoth

the fastest way would be transfering the potential energy difference to kinetic energy.

$$\Delta U=\frac{mv^2}{2}+\frac{mv^2}{2}$$

if they didn't have the same mass you had to use the momentum conservation eq. aswell.

Last edited: Jul 4, 2006