Explanation:
In order to calculate the force, we will use the following formula.
          F = [tex]k \frac{q_{1}q_{2}}{r^{2}}[/tex]
where, Â Â [tex]q_{1} = q_{2} = 3.0 \times 10^{-11} C[/tex]
        r = [tex]8.0 \times 10^{-5} m[/tex]
Therefore, we will put the given values into the above formula as follows.
         F = [tex]k \frac{q_{1}q_{2}}{r^{2}}[/tex]
          = [tex]9 \times 10^{9} \frac{3 \times 10^{-11} \times 3 \times 10^{-11}}{(8.0 \times 10^{-5})^{2}}[/tex]
          = [tex]1.265 \times 10^{-3}[/tex] N
Thus, we can conclude that the given two grains will repel each other by a force of [tex]1.265 \times 10^{-3}[/tex] N.
