Task 2

Materials and tools for a working group:

4 same jars with handles (buckets), sand, gravel, wood, stones, dynamometer

For stimulating situation, we recommend preparing 4 smaller buckets with different materials (eg sand, stones, gravel, wood). It is advisable to use different materials so that the pupils do not estimate the weight of the buckets according to how much material there is. It is sufficient to use smaller plastic buckets (bigger packages of yogurt).

The task will be to find out which bucket is the heaviest one. The teacher can use following instruction: Put buckets in order according to how much effort you need to lift buckets on a chair. Pupils can handle the buckets and propose the order according the perceived differences.

Differences in the weight of individual buckets should not be very large, so that subjective determination is not easy for pupils to do, but rather to get the feeling that they need a tool to find out the differences, by means of which we can determine the order accurately, or with which we can also determine differences in the strength we spend on raising the buckets. The teacher guides the pupils to try to figure out a procedure or a device directly to be able to tell with certainty which bucket is more difficult to lift and also to measure these differences. They are asked to write their proposals and list the tools they will need to try it. After completing the proposals, the teacher leads the pupils to present them to other groups. On the basis of the discussion, the pupils can adjust their proposals and then verify their functionalities. They will assess whether the proposed procedure able them to identify the differences between the effort exerted to raise the buckets.

Upon completion of the verification, the teacher suggests the pupils to investigate how differences in bucket weight can be measured using dynamometer. They recall how the dynamometer works and the results obtained by their own procedure are checked by comparing the weight of the buckets to the dynamometer. Since a dynamometer will be used to verify the proposed bucket mass measurement procedures, the bucket size and the amount of load compared will need to be adapted to what kind ofdynamometer the pupils will use.