Coulomb's law describes the magnitude of the electrostatic force between two electric charges. The Coulomb's law formula is:
  F = K_e * q1 * q2 / r²
Where:
  q1: Charge of object 1
  q2: Charge of object 2
  r: Distance between the two objects
  F: Force between the two objects. A positive force implies a repulsive interaction, while a negative force implies an attractive interaction
  K_e = Coulomb Constant, 8.9875517873681764 * 10⁹ N.m².C^-2

Coulomb's Law Examples:
What is the magnitude of the force between two protons which are 1.6E10^-6 meters apart?
The charge of 1 proton is +1e (+1.602E-19 C).
F = 8.9875517873681764 * 10⁹ * 1.602E-19 * 1.602E-19 / (1.6E-6 * 1.6 E-6) = 9 * 10^-17 N