'One of the most useful pieces of apparatus that a physics class could have. College/University level quality for higher precision and better results. Used to study linear motion under virtually frictionless conditions. Allows one to four carts to ride along on a cushion of air. 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. Photolight gate system complete with timer - light gates and accessories kit'