Purpose:Show that the sum of forces exerted on the mass by the scales is constant
Description:A weight is set on a platform scale, and the upper spring scale hooked to the weight. As an upward force is applied, the sum of the readings of the two spring scales remains constant, equal to the initial weight on the platform. In these photos, the sum of the forces on the 1kg mass remains slightly less than 10N as more of the lifting is transferred to the upper scale.