In the teaching of the principle of levers and pulleys, weights and balances have been used as conventional teaching aids. We have found, however, that we can use rubber bands instead of weights for this purpose, and have devised a simple experimental board using ordinary rubber rings and a scale by means of which pupils can perform various kinds of force experiments. (Fig. 2.7 ) By replacing weights with rubber bands we have found that this board is of advantage in presenting illustrative examples of force which an ordinary weight-balance apparatus fails to present. For instance, a lever model with its fulcrum at one end can be eaily made, and even the magnitude of the force exerted at the fulcrum can be shown by the number of stretched rubber bands. (Fig. 2.6 ) Besides being economical and easy to handle children soon get familiar with the apparatus because of their play experiences with rubber bands. It is to be noted that in the learning of force by our device, force is regarded as a dynamic tension produced by the expansion of rubber, rather than as a static gravitational force exerted. by the suspended weights. Thus we have introduced a new learning situation. The purpose of the present study was to attempt to construct and evaluate a more effective apparatus for the teaching of force and quilibrium. We have been also concerned with the sequence of the study in close relation to children\u27s understanding of force through their everyday activities. A preliminary study was made of 147 pupils (4th and 6th grades) at an elementary school. The procedures of the experiment and evaluation test were revised on the basis of an analysis of the findings in the preliminary study, and a later, full-scale experiment (using a "before-after" design) was made of 328 fourth-grade pupils of two different schools, each divided into four classes. In each school, two classes studied the principle of the lever with the rubber band apparatus, one being conducted mainly through teacher\u27s demonstration experiments and the other through pupils\u27 group experiments. The other two classes were used as control groups to cover the same subject using conventional apparatus (weights and balances). Several tests were given to examine the homogeneity of the four classes, and it was found that there were no significant differences among the classes. The findings obtained from the tests and the problems suggesting further investigation are summarized as follows: 1) The analysis of the before and after tests revealed that there was no significant difference in the effectiveness of learning between the "rubber band" groups and the "weight" groups, although there was a difference in the amount of learning between the two schools. This means that our teaching device was as effective as the conventional weight-balance apparatus. The precise functional difference in effectiveness of the two different approaches is still to be investigated further through continuing studies having more detailed design. 2) A correlation analysis, especially devised for this study, showed that there was a considerable amount of individual difference in the gains between before and after tests. The scores of the before test were negatively correlated with the gains. This means that the lower ability group in the before test made greater gains through this experiment. 3) An item analysis for the paired problems, one using rubber bands and the other with weights, indicated that these two types of learning were transferable, because both the "weight" and the "rubber band" groups equally gained on the problems using the material (rubber band or weight) which they did not actually use in the class
