P1.24. Force field experienced by a mass in the Earth's gravitational field. Assuming the origin to be at the center of Earth and the z-axis to be passing through the poles, write vector functions for the force experienced by a mass m in the gravitational field of Earth (mass M) in each of the three coordinate systems: (a) Cartesian, (b) cylindrical, and (c) spherical. Describe the constant-magnitude surfaces and the direction lines.