Title:

Students' use of representations in solving physics problems : complete and incomplete force diagrams

Physics concepts can be represented in many different forms such as verbal descriptions, sketches or pictures, graphs, diagrams, and equations. Force diagrams, or some say free body diagrams (FBDs), as physics representations are usually employed to teach and learn force concepts. Recent studies, which mostly have used quantitative approaches, indicate that the use of force diagrams can support or hinder students' performance in solving physics problems. This study investigates students' use of force diagrams when solving force problems. An interpretivist approach was implemented to answer four research questions including students' views about physics problem solving, students' views about representations, how students draw force diagrams when solving force problems, and students' views about drawing force diagrams. For data collection, surveys and interviews were conducted involving university students. A problem solving survey and representations survey aimed to obtain students' perceptions. Along with both surveys, two force problems were given to see students' performance in solving problems including their diagrams. Some students were invited to participate in individual clinical interviews, and later in paired interviews to obtain students' views about drawing force diagrams. The results show that most students viewed that mathematical knowledge as the most important element in solving physics problems and students often used representations for helping them to understand the problem and find the correct answer. Based on students' solutions, diagrams were categorised as complete, incomplete, and inappropriate. Students who drew complete diagrams tended to gain the correct answers in contrast to students who drew inappropriate diagrams. An interesting finding is that some students could solve problems correctly with drawing incomplete diagrams. From interviews, students asserted some reasons for drawing diagrams including to find the sign and direction of forces and to support in selecting mathematical equations. They recognised that physics and mathematical concepts are important in drawing force diagrams.
