# Coulomb's Law Question

I didn't use latex because for some reason, a term with the 10 to the power of -# isn't working properly:

$$1.0*10^-1$$

## Homework Statement

Two identical objects have charges +6.0 microcoulombs and -2.0 microcoulombs, respectively. When placed a distance "d" apart, their force of attraction is 2.0N. If the objects are touched together, then moved to a distance of seperation of 2d, what will be the new force between them?

Coulomb's Law

## The Attempt at a Solution

I solved for "d"
d =
sqrt{(9*10^9)(6.0*10^-6)(2.0*10^-6)
-------------------------------
(2.0)}

The d I got was 0.232m, so I doubled that to get 0.464m, since it says they would be at a distance 2d. Since they seperated from each other, then that means they are both the same charge.

FQ =
(9.0*10^9)(6.0*10^-6)(2.0*10^-6)
-------------------
(0.464)

= 0.2327N
approx. 0.23N
However, the answer at the back is "0.17N". What did I do wrong?

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Filip Larsen
Gold Member
You forgot to include the change in charge for each object as they touch.

I apologize, but I don't understand what you mean.

Filip Larsen
Gold Member
The problem text says " ... the objects are touched together". Think about what that means for the distribution of charge on the two objects.