Galactocentric gravitational force is used to model disk stars’ kinematics in the vertical direction. Stellar oscillation perpendicular to the galactic plane is modeled as simple harmonic motion (SH) made by the centrifugal force (Mach principle) opposite to the gravitational pull by the enclosed mass within the star’s galactic orbit. It was found that the galactocentric force of rotationally supported disks produces the observed stellar velocity ellipsoid tilt at all disk vertical distances in the solar neighborhood. The observed galactic rotational velocity at the solar location is used to obtain the galactocentric gravitational field of . The velocity ellipsoid tilt angles for the sun as well as stellar mid-plane velocities vs. maximum heights computed from SH model were compared with those computed from mass models of the Milky Way. It was found that a galactocentric potential alone that produces the stellar rotational velocity, with no adjusting parameters, describes well the kinematics of the disk in the vertical direction.