On the Moving Trajectory of a Ball in a Viscous Liquid between Two Concentric Rigid Spheres

In the paper, the dynamic motion of a point ball with a mass of m, sliding in a viscous liquid between two concentric spheres under the influence of gravity and viscous and dry resistance, is investigated. In addition, it is considered that the ball starts its motion from some arbitrary point M-0 = M (theta(0),phi(0)). A system of nonlinear differential equations in a spheroidal coordinate system is obtained for the angular variables theta and phi to account for all the forces acting on the ball. The dependence of the reaction force on the angular variables is found, and the solution of the resulting system of equations is numerically analyzed. The projections of the trajectories on the plane x - y, y - z, x - z are found.