Description: A set of four spring scales are hung from a stand. Each scale shows the total weight of those hanging below it plus any force exerted downward on the lower scale. The bottom scale measures its own weight, about 3 Newtons. In the picture above, a downward force of 9 Newtons is being exerted by Jack's hand at the bottom of the picture, so the scales read (bottom to top) 12N, 12N, 15N, and 18N.
