To demonstrate that the relationship between the extension on a spring is proportional to the load applied to it. This complete apparatus has a 150mm adjustable mirror scale to prevent parallax error and is marked in millimeters and mounted on a sturdy 300mm rod. Attached to the rod is a hook supporting a coiled spring with a mass hanger and indicator. Supplied complete with a 250g slotted weight set, the apparatus is mounted on a wooden base.