The Principles of Technology II classes built roller coasters out of cardboard, glue sticks, construction paper, Popsicle sticks and a marble.  The roller coasters were required to have at least 3 hills and the marble had to return to the bottom of the starting hill.  When the roller coasters were complete, the students calculated the potential energy and kinetic energy of each roller coaster and discussed how important potential energy and kinetic energy were in the success of each roller coaster.