Description:A small mass hanging over a frictionless pulley provides the constant force which accelerates the glider between gates A and B. Using the photogate timing system, the time for the glider to travel from A to B can be measured, or the velocities of the glider at positions A and B can be measured using the 5 cm tab mounted on the glider. The accelerating force can be varied by adding additional masses, or gliders of mass M, 2M, and 3M (2M + M) can be used. A careful measurement should yield a result good to <10%.