## College Physics (4th Edition)

The correct answer is: (a) $\frac{F}{2}$
We can write an expression for the original force: $F = \frac{k~q_1~q_2}{r^2}$ We can write an expression for the new force: $F' = \frac{k~(2q_1)~q_2}{(2r)^2} = \frac{1}{2}\times \frac{k~q_1~q_2}{r^2} = \frac{F}{2}$ The correct answer is: (a) $\frac{F}{2}$