This activity is an excellent student-centered, problem solving based project. This pairs great with the standards covered in NGSS MS-PS3. It has students build a roller coaster applying what they have learned about potential and kinetic energy. It can be used to supplement instruction on PE and KE, or could serve as a performance assessment. This project has always been one of the highlights for my 7th graders. The materials for this project are of minimal cost and include: pipe insulation tubing, masking tape, and marbles.