M. 310. Put a ping-pong ball onto the surface of the water in a glass, filled halfway. We experience that the ball moves next to the wall of the glass. Then fill the glass up to its rim, and place the ball again to the water. We can see that the ball moves to the centre of the glass. Examine experimentally, whether we experience the same or not if instead of the glass we use a wider vessel, for example a pot? What is the width of that vessel in which the experiment still ``works''? How does the time during which the ball moves to the wall, depends on the initial distance between the ball and the wall?
Deadline expired on 10 January 2011.