The gravitational field due to a point mass M may be obtained by analogy with the electric field by writing an expression for the gravitational force on a test mass, and dividing by the magnitude of the test mass, m, Show that Gauss' law for the gravitational field read where G is the gravitational constant. Use this result to calculate the gravitational field at a distance r from the center of a sphere of radius R and uniform density for r > R and for
