this is about Electrostatics

Answer:
Force, [tex]F=2.88\times 10^{-3}\ N[/tex]
Explanation:
Charge 1, [tex]q_1=1\times 10^{-7}\ C[/tex]
Charge 2, [tex]q_2=-2\times 10^{-7}\ C[/tex]
Distance between charges, d = 0.25 m
It is required to find the force between charges. The charges are opposite the force between them is attractive. The force between charges is given by :
[tex]F=\dfrac{kq_1q_2}{d^2}\\\\F=\dfrac{9\times 10^9\times 1\times 10^{-7}\times 2\times 10^{-7}}{(0.25)^2}\\\\F=2.88\times 10^{-3}\ N[/tex]
So, the force between charges is [tex]2.88\times 10^{-3}\ N[/tex].