A System Schema Tool to Promote Understanding of Newton's Third LawSeveral years ago, the Modeling Instruction Program at Arizona State University developed a representational tool called a "system schema" to serve as a conceptual bridge between simple pictorials and more abstract representations (such as free-body diagrams). A system schema consists of identifying and labeling all objects of interest from a given physical situation, as well as all the different types of interactions between the objects. Use of system schema has been tested in classroom settings and is associated with significant performance gains in applying Newton's Third Law.
Physics by Discovery: Interaction Force PairsThis 8-minute video by HS physics instructor Karen Hunter shows how to draw a "System Schema", as described in the article above. It does a nice job of differentiating interaction force pairs and force representations in a free-body diagram. The explanation is especially strong in its treatment of the normal force, an area of documented misconception among learners. We recommend this video for your visual learners and for students who are struggling with the content.