Calculate Electrostatic Force: Metal Spheres 3.00x10^-6C & 2.00x10^-6C @12.0cm

[Aamun]

Homework Statement

A metal sphere with a negative charge of 3.00x10^-6C is placed 12.0 cm from another similar metal sphere with a positive charge of 2.00x10^-6C. The two spheres momentarily touch, then return to their original positions. Calculate the electrostatic force acting on the two metal spheres.

Homework Equations

Fe=kq1q2/r^2

The Attempt at a Solution

Fe=(8.99x10^9)(3.00x10^-6)(2.00x10^-6)/(.12^2)
Fe=3.75 N [Repulsive]

For some reason the above formula won't work to get the answer that it says, am I doing something wrong?

Answer should be 1.56x10^-1 N [Repulsive]

 

[Oerg]

what happends when the 2 charges touch? Charge is transferred, therefore you have to find out the final charge on eache sphere before you can use the formula.

 

[Aamun]

Oh yeah! Ok thanks I got it now!