# Homework Help: Coulomb's law problem

1. Jun 20, 2014

### buoya

1. The problem statement, all variables and given/known data

Two small spheres of charge 10Q each separated by a distance d repel each other with a force F. In terms of F what would be the new repulsive force if 2Q were removed from one sphere and added to the other?

2. Relevant equations

F = kQq/r^2

3. The attempt at a solution

F = k(10Q)(10Q)/d^2 if 2Q were removed.... F = k(12Q)(8Q)/d^2

Is that the answer? it seems too easy

Thanks for any input!

2. Jun 20, 2014

### nasu

You need to find what fraction of F is the new force. Just one more step to do.

3. Jun 22, 2014

### dauto

Your answer is correct but is not "In terms of F". Tip do not use the same symbol "F" to represent two different quantities. If the original force is F than the new force could be any of f, F', F2, or even G. But it is not F. F is already taken.

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