PUPILS’ MENTAL MODELS OF A PULLEY IN BALANCE

Pupils from 5th, 7th and 9th grades compared the weight of a small standard mass and a big bag hanging in a pulley at different positions in equilibrium. In all the three age groups the majority (about 70%) of the pupils stated that the lower hanging bag is heavier. Less than 15% of the pupils in the 7th and 9th grades understood that the bodies must have the same weight. Pupils' reasoning was classified into four categories that were interpreted as mental models according to Vosniadou's framework theory. Only about 5% of the seventh graders and 10% of the ninth graders seem to grasp the scientific model Motion that leads to the concept of gravity.