Planets are not uniform inside. normally, they are densest at the center and have decreasing density outward toward the surface. model a spherically symmetric planet, with the same radius as the earth, as having a density that decreases linearly with distance from the center. let the density be 1.60 x 10^4 kg/m^3 at the center and 2100 kg/m^3 at the surface.
what is the acceleration due to gravity at the surface of this planet?