Question

There are two charged particles. They exert an electrostatic force of 10 N on each other. Suppose the distance between the two particles is increased to five times the original distance. What will the magnitude of the force?

Answer 1

since F = qq/r^2, changing r to 5r means you now have

qq/(5r)^2 = qq/25r^2 = 1/25 * qq/r^2 = 1/25 F