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

Task 3b

WORKSHEET

Materials and tools for a working group:

4 pendulums with various lengths of string (10 cm, 20 cm, 30 cm, 40 cm)

In order to practice the ability to work with the graphical representation of the measurement results, students are asked to solve the problem 3b. Intentionally, this time the columns are horizontal so that the pupils realize that no matter which direction the diagram is oriented to, they just need to be well marked. The task of the pupils is to create four pendulums of different string lengths, exactly as shown in the diagram. If they already have a measurement result with some string length, they do not need to repeat it, the results overwrite the chart again and complete the missing data. In this way, they obtain more results binding to the phenomenon under investigation. In the diagram, they should see how the number of oscillations decreases with the extension cord on the pendulum.

The individual results for pendulums of the same string length obtained in different groups may differ. If they differ significantly, it is likely to be due to measurement inaccuracy and /or the measurement was accomplished slightly different way. It is good to point out such differences and try to find out, together with the pupils, what caused the differences in the results. In this case, the pupils present themselves how they realized the measurement and identify what they did differently and thus what caused a difference in the measured vibration counts. If the reason for the different results could not be identified, it is advisable to repeat the frontal measurement. The credibility of the results obtained is very important. If it is not high enough, the pupil will cease to believe in the outcome and does not tend to perceive the results of the examination as plausible and does not incorporate them into their ideas as other experiences. As a result, the pupil is unable to use this information later to explain similar observed phenomena.

Finally, the teacher will focus pupils‘ attention on whether the results of the examination in task 3b are consistent with the results obtained in the previous task, i. whether these results confirm what they found in the previous review.