Body forces Body forces: the forces can work at a distance and depend on the amount of material affected, so, we can call body forces distant forces. Gravitational force is an example of body forces. The gravitational force on a rock body of mass m is F=m where g is the acceleration of gravity. g varies with depth in the earth and with position on the earths surface, but for the purpose of structural geology, it is a constant 9.8m/sec2Body forces: the forces can work at a distance and depend on the amount of material affected, so, we can call body forces distant forces. Gravitational force is an example of body forces. The gravitational force on a rock body of mass m is F = mg where g is the acceleration of gravity. g varies with depth in the earth and with position on the earth’s surface, but for the purpose of structural geology, it is a constant 9.8m/sec2 . Body forces