Task 28

Materials and tools for a working group:

Force gauge, weight, water tank

The teacher reminds pupils that they have explored different situations in which it is sometimes possible to move with the same object relatively difficult and sometimes very easy (sometimes it seems heavier, sometimes less heavy). He asks students about such situations, either from previous research or from their previous experience. The discussion leads to a situation where most of the pupils are likely to have the experience of lifting objects under water and above water. He will present this situation as one of those things where the same objectonce seems lighter and sometimes harder. He suggests that they examine it better and see if the object is actually lighter in the water.

In this task, pupils do not propose the procedure, it is already intentionally given, so that the pupils become familiarized with the dynamometer, which they will later use when examining the functionality of simple machines. It is suitable if the teacher shows the dynamometer to the pupil before performing the task. He may not explain how if it works, as its use is fairly intuitive. In order to make sure that pupils understand how it is used, he will ask them to try to explain how they would use this tool to find out whether objects in water are lighter than outside water. Subsequently, the pupils will be provided with water containers, and the pupils will find out whether the object (weight, sinker) will cause the spring of the dynamometer to be stretched equally when the object is in water as it is above its surface. After the observation, they evaluate what they found.