Answer:
90 N
Step-by-step explanation:
The electrostatic force between two charges is given by:
![F=k(q_1 q_2)/(r^2)](https://img.qammunity.org/2020/formulas/physics/high-school/itwxhnt3zxt9ptmy812nb6j3yub8evq9o1.png)
where
k is the Coulomb's constant
q1, q2 are the two charges
r is the separation between the charges
In this problem we have
q1 = q2 = 0.005 C
r = 50 m
So the electrostatic force is
![F=(9\cdot 10^9 N m^2 C^(-2))((0.005 C)^2)/((50 m)^2)=90 N](https://img.qammunity.org/2020/formulas/physics/college/ysdl9dg4q4tsmvk7uqifx1bezlxthwmqsh.png)