This is one of the most useful pieces of apparatus that a physics class can have. This air track allows one to four carts to ride along on a custion of air, practically eliminating friction. High precision pulleys are included to mount on the ends for performing free falling and incline experiments. Spring bumpers can be attached to record impact forces and weights can be attached to each cart for studying momentum and many other phenomena's involving force. The air source is not included. The unit can be used with our photogates and digital timer (recommended) and our quiet air source.