Answer:
Force, [tex]F=8.71\times 10^{-4}\ N[/tex]
Explanation:
Given that,
Charges on pith balls, [tex]q_1=q_2=-28\ nC=-28\times 10^{-9}\ C[/tex]
Distance between balls, d = 9 cm = 0.09 m
Let F is the repulsive force between two pith balls. We know that the repulsive force between two charges is given by :
[tex]F=k\dfrac{q_1^2}{d^2}[/tex]
[tex]F=9\times 10^9\times \dfrac{(-28\times 10^{-9})^2}{(0.09)^2}[/tex]
F = 0.000871 N
or
[tex]F=8.71\times 10^{-4}\ N[/tex]
So, the repulsive force between the pith balls is [tex]8.71\times 10^{-4}\ N[/tex]. Hence, this is the required solution.