3 CHANGING THE MOVEMENT OF AN OBJECT REQUIRES A NET FORCE TO BE ACTING ON IT

Task 9

Materials and tools for a working group:

pulley from previous task, pulley with larger wheel, bucket with load

In the previous task, pupils found that using a free pulley can reduce the effort to pull the load up. The ninth task addresses a new research question: Does the magnitude of the force that we lift a load with a free pulley depend on how big is the wheel we use on the pulley? Pupils formulate predictions and verify them by constructing two pulleys using differently sized wheels. Since they have found in the previous task that a fixed pulley does not reduce the force used, it is necessary to construct free pulleys. Also, it is important to discuss with pupils what and how you need to measure and also have a pre-thought when the predictionscan be confirmed. I what results need to be obtained in order to confirm or not to confirm the difference in force that needs to be exerted to pull the same load with free pulleys with an unevenly large wheel.

The conclusion of the investigation is formulated in the form of an answer on the research question. In carrying out the verification, it is important to alert the pupils to the same constant conditions of verification (working correctly with the variables of the examined situation) – to use the same twine, the same smooth pulley surfaces, the same high cost, and so on, so that any difference between the two pulleys caused only by the size of the wheels used on the pulleys is actually found. A sense of working with variables is only being developed by these activities at the first stage of primary school, so it is often necessary for the teacher to direct pupils to be careful about setting comparison conditions.