Place a few balls in a round container. If you move the container around a vertical axis, the balls can move codirectionally with the movement of the container, or they can move in the opposite direction. Explain this phenomenon and investigate how the direction of movement depends on relevant parameters.

将几个球放在一个圆形容器中。 当围着一个垂直轴移动容器时，球可能发生与容器移动同向的运动，也可能反向运动。 解释这种现象并研究运动方向如何取决于相关参数。