Task 5

Materials and tools for a working group:

closeable jars of the same size, water, material to create an isosceles lever (eg plate and triangular prism)

The fifth task is to clarify the use of the lever as a simple machine. Pupils solve the research question: What does it depend on whether two objects on two opposite sides of an isosceles swing will be in balance or not? The taskuses closable jars of the same size with a various amount of water (full and half-empty cup), so that the situation in the pupils evokes the concept of differentlyweighted but equally large objects.

Three positions are indicated on the isosceles lever, which the pupils can mark with numbers in order to be able to speak about the observations and results of the observation. It is advisable to use a thinner plate, but not so thin as to bend; and adequately long. Swing must be tested beforehand in order to detect differences arising from the worksheet. If the swing is too short (the spacing of points 1, 2 and 3 on which the cups are placed is small) and the board is relatively thick, balancing with glasses of different weights may not be accurate.

Pupils make predictions. In particular tasks, they must observe not only the place of the isosceles lever, where the jars are placed, but also whether the jars are full or half empty. The simpler task is to create predictions where the task of pupils is to indicate in which situations the isosceles lever (swing) will be balanced. Pupils express predictions by marking these situations. A more difficult task is to assume which side of the lever will be tilted if the isosceles lever is not balanced. Students can record this predictions with a green arrow directly into the images.

It is advisable if the teacher asks pupils to justify the predictions. It is enough if he puts questions when presenting predictions (frontal or individual in each group when preparing predictions): What do you think? Do you have the experience that supports your prediction? The reasoning of the stated prediction develops the skills of making predictions, the predictions differ from the guesses, as they are justified by at least pupils´ own experience or knowledge. Because the predictions are justified, the research itself is functionally linked to previous experience, and at the same time pupils perceive that research helps them to clarify commonly observed phenomena.