It's important that children observe something. In this case a vortex - and manifestation of the Coriolis Effect. Then try to understand WHY it happens the way that it happens.
|Griffin applies Newton's Laws applied to a rotating system.|
The Coriolis force acts in a direction perpendicular to the rotation axis and to the velocity of the body in the rotating frame and is proportional to the object's speed in the rotating frame. The centrifugal force acts outwards in the radial direction and is proportional to the distance of the body from the axis of the rotating frame.
The Coriolis effect is caused by the rotation of the Earth and the inertia of the mass experiencing the effect. This force causes moving objects on the surface of the Earth to be deflected in a clockwise sense (with respect to the direction of travel) in the northern hemisphere, and in a counter-clockwise sense in the southern hemisphere -- which is why the toilet water flows "the other way" when you cross the equator, and flush.
This is the project for a Sunday Morning.