The cars will work very well on tile floors and carpeted floors with a short nap. Several tables stretched end to end will also work, but cars may roll off the edges. Although this activity provides one car design, students can try any car shape and any number, size, and placement of wheels they wish. Long cars often work differently than short cars. In this case, the payload of the balloon rocket is the car.
Wheels reduce friction with the floor to help cars move.
Because of individual variations in the student cars, they will travel different distances and often in unplanned directions. Through modifications, the students can correct for undesirable results and improve their cars' efficiency. If you are going to have them construct a second car, tell them to save styrofoam tray scraps for later. Hold back the additional materials for the second car until students need them. Students should plan the arrangement of parts on the tray before cutting them out.