Shown on top of Force Table, no. 1874. An attachment for use with our force Table, useful for study of static equilibrium of a rigid body under the action of forces, all in the same plane, Two 25-cm aluminum discs of thickness 8mm are separated by 3 steel balls. A removable peg in the lower disc protrudes through an enlarged opening in the upper disc. Thus, the upper disc is free to move horizontally until constrained by the peg. The upper disc has several holes of take pegs whose positions can be changed. The disc arrangement is mounted on top of the force table. Included are 2 aluminum discs, set of 4 metal lugs to fit holes on the upper disc set of 4 strings with metal rings at both ends, 3 ball bearings, and arrangement for raising the pulley brackets to compensate for the height of the plate attachment, instructions included.