ABSTRACT
Once again our subjects are given an equilibrium problem; one not too different from the balance problem but especially designed to bring out work relationships. A toy dumping wagon is drawn along a rail whose inclination can be varied. The task is to predict the movements or equilibrium position of the wagon as a function of three variables—the weight it carries, the counterweight suspended by a cable fastened to the wagon, and the inclination of the track. This last variable is calculated not in terms of its angle measured in degrees, but in terms of its sine—i.e., of the (variable) height h. Thus, the law of equilibrium to be found is W/M = h/H, where W is the (variable) counterweight, M the weight of the toy wagon (which itself weighs 4 units, but which can be loaded with varying amounts of weight), and H the total height (the unvarying length of the track assuming it is held vertically).
