Movement of Charged Particles in a field

[Karma]

Homework Statement

Two electrons are 10-9m Apart when they are released.What is their speed when they are 10-8m apart?

Homework Equations

Ek=-EE
EE=Kq1q2
-------
r

The Attempt at a Solution

Ive tried 1/2mv^=-(Ke(squared) - Ke(squared)
------------ -----------
r2 r1
And i don't seem to get the answer
By the way the answer to the question is 4.78x10^5 m/s
thanks for the help

 

[mace2]

Calculate electric potential energy when they are 10^-9m apart, and then when they are 10^-8m apart. The change in energy has become kinetic energy, and you may calculate it from this.

 

[Karma]

I did that.. And i still get the wrong answer but its pretty close.. i guess its a calculation error.. i will go back and recheck thanks for the help...

 

[mace2]

Yeah doublecheck your calculation. I did it and I got something like 4.79e5, so I'm pretty sure that's how you do it.