Answer:
New force = 9(initial force)
Explanation:
The force between two charges is given by :
[tex]F=\dfrac{kq_1q_2}{r^2}[/tex]
Where
d is the original distance
Let d' is the new distance such that, r' = r/3
New force,
[tex]F'=\dfrac{kq_1q_2}{r'^2}\\\\F'=\dfrac{kq_1q_2}{(\dfrac{r}{3})^2}\\\\F'=9\times \dfrac{kq_1q_2}{r^2}\\\\F'=9F[/tex]
So, the new force becomes 9 times the initial force.