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B) Teaching with Experiments |
Guidelines for the teacher This experiment offers the opportunity to discuss about the effect of the medium on the way various weights fall. The teacher could start a discussion about the way bodies of various weights fall in everyday life and how bodies reach the ground not at the same time when let go from the same height, but first the heavier ones hit the ground. Then the teacher could ask the students what would happen if there weren’t the medium (the air, the atmosphere) and the fall was taking place in vacuum. Would bodies let fall from the same height touch the ground at the same time? Then the teacher could invite the students perform the “experiment with everyday materials” that is based on Galileo’s experiment that focused on making people aware of the effect of the medium on free fall. The teacher performs the experiment in the classroom following the steps described in the section “Experiment with everyday materials”. He encourages the students to focus on the time interval between the hits on the bottom of the bottle-tubes of two balls with different weights. The lighter the medium the shorter this time interval is and in the air the two balls hit the ground simultaneously. Every time before letting the balls go the teacher asks the students to make a hypothesis about the time each ball would hit the bottom and the duration of the time interval between the two hits (will it be the same, shorter, longer?). Finally the teacher lets the balls fall in the air and asks students to comments on the various phases of the experiment. The experiment could also be carried out by the students in small groups in a laboratory session instead of the teacher performing the experiment. In this case the teacher encourages and the organizes the discussion in the groups and in the classroom.
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