Analysis of force representation categories and representation patterns by force type in high school students’ free-body diagrams

This study analyzes free-body diagrams (FBDs) drawn by 100 high school students to identify patterns of thinking about forces and explore how gravity, elastic force, friction, hand-applied force, and vertical/horizontal normal forces are recognized and represented. Representations are classified as object-centered, agent-centered, or contact surface-centered. Gravity is mainly object-centered, friction is contact surface-centered, while the other forces, including normal forces, are agent-centered. Misconceptions included seeing gravity as acting throughout space, confusing the direction and application point of elastic force, believing hand-applied forces could penetrate objects, and a high omission rate for friction. The results show FBDs as effective tools for diagnosing students’ conceptual understanding and emphasize the need for explicit instruction on points of application and identifying the body receiving the force. The analytic framework and dataset also provide a basis for AI-based diagnostic and personalized learning support in physics.