| The Gravitational Force:
between any two masses in the universe.
|The force of gravity is one of the fundamental forces in nature.
Material objects attract pairwise with a force that is proportional to the masses and inversely proportional to the square of the distance between them.
|between the Earth and the Moon
|It can be shown that the force of attraction between homogeneous spherical objects is given by the same expression as the force between two point masses, provided the distance is taken from the centers of the spheres.|
Satellite in a circular orbit.
|A circular orbit is a special case. In general, a closed orbit is an ellipse with the center of attraction at a focal point. In that case the gravitational pull does not equal the centripetal force and the satellite has a tangential acceleration.|