A foam-tube marble roller coaster is an easy-to-make educational toy that will teach your child about velocity, potential and kinetic energies, gravity, friction and slope. Two roller coasters is an invitation to friendly competition.
Cut each length of foam pipe insulation into two U-shaped sections. The tubes will have a factory cut nearly through already. Complete that cut and then cut directly across.
Tape the two pieces end to end so that you have a 7.2 m (24 foot) U-shaped length of foam insulation.
Tape one end of the foam channel to a wall about 1.2 m (4 feet) from the floor.
Construct the roller coaster by bringing the foam from the wall to the floor at a steep angle and then forming a 30 to 50 cm (12 to 20 inch) loop. Tape the edges of the loop together. Make a stack of books on the floor and pass the foam over them, forming a hill. Continue making loops, turns and hills as desired.
Drop a marble through the channel starting at the wall. Experiment with the angle of the initial drop and the steepness of the hills until the marble will complete the track.