浮力教材の開発と中学校における授業実践

抄録

We have developed teaching materials to directly measure the buoyant force of a body, using an equal-arm balance. First, to cancel the gravity effect, we made the arm of balance horizontal by attaching the body and an appropriate weight of clay at each end of the arm in the air. After this, we immersed the body in water. The body, being exposed to buoyancy only, floated. Next, we made the arm of balance horizontal again by pushing down the body-side arm with an electric balance. Thus, the display of the electric balance has been arranged so as to stand for the buoyant force of the body. We implemented a class practice at a public lower secondary school with these teaching materials for encouraging students to understand that the buoyant force of the body depends on the volume and is independent of its position, shape, and mass. The results are as follows: Students’ understanding for the contents of buoyancy treated in the practice improved. Furthermore, improvement of students’ understanding is also useful for buoyancy problems which are concerned with moving bodies and with boards in different situations of position and direction, which were not treated in the practice.