Abstract:

In response to traditional physics laboratory, used mainly to test theories seen previously through lectures, we advocate a more interactive laboratory where students can develop knowledge under teacher’s supervision. In this approach, called "guided discovery", learning in the laboratory results from activities where students proposed their ideas about properties of acceleration and test them through experiences. Consequently, we designed a scientific investigation approach that takes into account students' alternative conceptions with respect to acceleration and allows them to verify their hypotheses in the laboratory. Written in the format of a prediction-observation-explanation (POE) tasks, each task consisted of three stages, each stage corresponding either to prediction, observation, explanation. Only the results of the prediction part are reported here.

Thus our research aimed to diagnose students’ alternative conceptions about acceleration while they are interacting with two concrete set-ups. In the first set-up, a ball is placed at the top of an inclined track. The students are asked to predict what will happen to the position, speed, and acceleration of the ball when it is allowed to roll downward without initial speed. Similar questions are asked to the students about the second set-up, where a ball is thrown up an inclined plane.
Our pilot study included a class of 23 francophone students in grade 11 physics from a Canadian school. The students in this class chose the science orientation offered by the school so that it is fair to say that they are interested in science in general and physics in particular. The teacher involved in this research had 20 years of experience teaching science. To study the students’ conceptions about acceleration, we analyzed the content of the activity guide students had to fill.

Content reported by students in these guides were expressed in different ways: text when answering questions, iconic in sketches of the moving ball. Qualitative data collected in these various forms of presentation received a categorization analysis. In results section, we identified the main alternative conceptions of students of the acceleration in rectilinear motion. Among these, we identified representations that reveal confusion between speed and acceleration, their graphs with respect to time often drawn in a similar way. Other aspects, for example when the ball that is thrown upward an inclined plane, the graphs drawn by students of position, speed and acceleration with respect to time, revealed that some did not include progressive deceleration nor did they mention the annulation of the speed at the highest point of the trajectory. Finally, we conclude by specifying the advantages and limits of our research, as well as recommendations for further research.

Keywords:

Acceleration, alternative conceptions, POE task, high school physics, laboratory.