The hydrogen atom consists of a proton of mass 1.67 ˛ 10-27 kg and an orbiting electron of mass 9.11 ˛ 10-31 kg. In one of its orbits, the electron is 5.3 ˛ 10-11 m from the proton. What is the mutual attractive force between the electron and proton?

Newton's law of universal gravitation: Every particle in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distances between them. This force acts along the line joining the two particles.