Dynamic Stabilization of Water Bottles

The motion of water filled bottles is studied when it is thrown into the air and falls back to the floor, including the possibilities of an upright landing or rolling down before it finally reaches static state. When dealing with the process after throwing a water bottle, the free falling (bottle falls without initial angular velocity) and flipping (bottle falls with initial angular velocity) are considered. In theory, the physical principles behind the motion are analyzed. In addition, the impacts of initial angle, linear velocity, angular velocity and the water amount on the uprightness of the bottle are discussed. In experiment of throwing bottle, we changed the water amount, angular velocity, and releasing height, and examined the impacts of these factors. The results suggest that a certain amount of water and spinning result in higher possibility of upright landing. When dealing with rolling bottle, theoretically we build the bottle-and-bead model to describe the coupled motion of water and the bottle. Analytical solutions are obtained for small amplitude and the numerical solution can be done in a general situation. In the experiment of rolling bottle, we firstly verified the theoretical model, and then addressed the impact of initial conditions and water amount on the motion patterns of the bottle.