In a solid sphere of radius R the density ρ is a function of r, the distance from the center of the sphere. If the magnitude of the gravitational force of attraction due to the sphere at any point inside the sphere is kr2, where k is a constant, find ρ as a function of r. Find also the magnitude of the force of attraction at a point outside the sphere at a distance r from the center. Putnamfunctiongeometry3D geometryspherephysics