Cut both pieces of 6-foot, 1 1/2-inch-diameter foam pipe insulation in half lengthwise so they form a "U" shape. Each pipe comes partially cut. Cut the partially cut side all the way through, then cut the opposite side to create two U-channel pieces per pipe. You should have four U-channel pieces in total with this step.
Tape two pieces of foam track together with masking tape. Be sure the tape is smooth inside the foam tube and the channel is on the inside. Curl the track to form a loop, approximately 12 to 20 inches in diameter. Use a ruler to measure its width. Tape the loop you formed together where the two tracks meet.
Tape a third section of track so it connects to one side of the loop. Secure a fourth section of track so it connects to the other side of the loop with the tape. Be sure the tape is smooth inside.
Raise one end of track up to a bookshelf or table and tape it down with the masking tape. The loop should sit on the floor. Tape it down to the floor.
Measure the diameter of the loop and the height of the track where it meets the bookshelf or table. Measure the total distance of track from the bookshelf to the loop.
Perform a simple experiment in the transfer of potential to kinetic energy by releasing a marble from the top of the roller coaster and watching it travel down and around the loop. You may need to adjust the height of the initial drop so the marble can make the loop.