Force between conducting spheres

[dekonig]

X and Y are two identical conducting spheres separated by a distance d. X has a charge of +6µC and Y has a charge of -2µC. The electric force between them is +F (i.e. attractive). The spheres are touched together and are then returned to their original separation d. What is the new value of the force between them?

Any help is greatly appreciated. I assumed that since the net charge should remain the same after, there would be no change in the value of the force, but the answer scheme gives the answer as -F/3.

 

[ehild]

What happens with the charge if the conducting spheres touch each other?

 

[dekonig]

thanks for the reply man, i think i got it. The charges become +2µC on both sphere X and Y, at which point it's just subbing the before and after values for the charge into F=(kq₁q₂)/r², and since, they're now like charged, the force becomes a repulsive one, hence -F/3