Effectively and economically explore the laws of motion without an air table. Study inertia, constant velocity and acceleration, and collisions in two dimensions. Air escaping from the inflated balloons allows these plastic pucks to levitate above any smooth surface. Two pucks can easily be stacked together to double the mass. Alternately, pucks can be opened and washers can be added to the mid-section of the pucks to change the mass of the finished puck. Set includes two large (45 g) pucks, two small (29 g) pucks, four balloons and four nozzle adapters.