disc rolling uphill.
The disc has a lead weight hidden in the rim. When it is placed on an inclined plane, it might roll down the plane. However, if the concealed loaded region is properly oriented so that its potential energy minimum lies up the plane, the disc will surprisingly roll up the plane. If the disc is released near the edge of the lecture bench, it will roll to the edge, stop before going off the edge, and then roll back.
|disc with a hidden lead