# Homework Help: Electrons Colliding - Totally Confused

1. Jan 2, 2012

### Millacol88

1. The problem statement, all variables and given/known data
Two electrons separated by a large distance are fired directly at each other. The closest approach in this head-on collision is 4.0 * 10-14 m. One electron starts with twice the speed of the other. Assuming there is no deflection from the original path, determine the initial speed of each electron.

2. Relevant equations
Ee = kq1q2 / r
Ek = 1/2 mv2

3. The attempt at a solution
I'm really lost as to how to start this. It must have something to do with electrical and kinetic energy but other than that I am mystified as to how to solve this.

2. Jan 2, 2012

### technician

My first step would be to calculate the potential of 2 electrons at the given separation (equation 1)
The total KE would then be equal to this as the next step

3. Jan 3, 2012

### Millacol88

OK, so I'm getting the velocities as 1.0 * 108 m/s and 5.0 * 107 m/s. I'm pretty confident about this but the textbook only gives one answer (5.3 *7 10) m/s. There should be two velocities as an answer, so I think that must be an error. Is my answer correct?

4. Jan 3, 2012