Abstract:

Students during the problem-solving process in the subject of Statics have difficulty in constructing the free-body diagram on statically determined beams. Free-body diagrams are graphic representations used in mechanical problems involving forces and moments. The errors students show is due to the presence of alternative conceptions. These generate a conflict in the construction of the free-body diagram of a beam subjected to different types of load and to different types of configurations. Therefore, the purpose of this study was to change the alternative conceptions presented in the study of statically determined beams using the refutational text to improve the performance of students who are taking the subject of Static offered by an Ecuadorian public university. The alternative conception under study is as follows: Students when they make the free-body diagram of a simply supported beam under the action of concentrated loads with a certain inclination think that the roller support has a vertical and horizontal reaction. To promote the conceptual change in this case, the refutation text was used, which is the appropriate strategy to achieve it, and which is proven to change the alternative conceptions that students have. The refutation text has two components: the presentation of the alternative conception to be changed and the explicit refutation of the alternative conception using the commonly accepted scientific arguments. The importance of the refutation text as an agent of conceptual change must provide a compelling argument for inducing conceptual conflict. That is, the discrepancy between right and wrong. The refutation text must be well written in such a way that the student understands the difference between the exact and inaccurate. The participants were 66 students, aged between 18 and 20 years. The instructional unit was "Force in Beams". The time devoted to the teaching lasted eight hours. The material delivered was the refutation text. The evaluation instrument had four problems, two of which specifically assessed the presence or not of the alternative conception. The procedure followed in this study was as follows: Explain the unit of forces in beams to both the experimental and control groups. During the teaching process, students from both groups were asked to solve a problem of a simply supported beam, subjected to a concentrated load inclined at a certain angle. The refutation text was then delivered for reading and group discussion only to the experimental group. Finally, the posttest was administered to both the experimental and control group. This test not only evaluated the correct construction of the graph but also the calculation of the reactions. The results of this study focus first on how many students in each group incorrectly made the free-body diagram on the pretest. In the pretest 26 students of the control group and 28 of the experimental group incorrectly made the free-body diagrams. In the posttest the students of the control group made 43 free-body diagrams correctly while the students of the experimental group made 60 free-body diagrams correctly. The Gosset test gave a value of t = 2.94 with 62 degrees of freedom and a p-value of 0.0046. The results show that the refutation text promotes the conceptual change in the alternative conception studied. This was achieved because of the quality of the arguments presented to change the alternative conception.

Keywords:

Alternative conceptions, conceptual change, refutation text, statically determined beams.