Answer
The gravitational force governs the motion of planets in the solar system.
The gravitational force is the weakest of the fundamental forces.
Work Step by Step
The gravitational force governs the motion of planets in the solar system. The gravitational force between the sun and each planet keeps each planet in orbit around the sun.
The gravitational force is the weakest of the fundamental forces. However, the strong force and the weak force only operate over very tiny distances, such as the distances within atomic nuclei. The electromagnetic force, although stronger than the gravitational force, does not govern the motion of planets in the solar system because it is not interactions of electric charges nor interactions with a magnetic field which govern the motion of the planets.
