After brushing, Fluffy's fur has a charge of + 8.0 * 10-9 coulombs and her plastic brush has a charge of - 1.4 * 10-8 coulombs. If the distance between the fur and brush is roughly 5.0 * 10-1 meters, what is the approximate magnitude of the force between them? (k = 9.0 * 109 newton·meters2/coulomb2)

The equation in Coulomb's law is F = {k*q1*q2}/r^2 where F is the force between charges, k is a constant, q1 is the charge of the first particle, q2 is the charge of the second particle and r is the distance between the two particle charges.

Substituting to the equation:

F = k*q1*q2/r^2 = { 9x10^{9} * 8x 10^{-9} * - 1.4x10^{-8} } / ((5x10^-1) ^2)

= - 4.032x10^-6 Newtons