A figure has been added to clarify the geometry of the problem. Moreover, additional discussion of the trajectories involved are now given in paragraphs that were added to help explain the plots given in Figures 2 and 3.
The relative location of the test mass to the cold atom cloud should be clearly stated during the calculation, as the gravitational force is a vector. If the test mass is not located in the direction of the evolution trajectory of the atom cloud, the applicability of some formulas (e.g. Equation (3)) need to be verified. It will be helpful to the readers if a figure is provided to show the locations.