PHYS.5.G
The student is expected to illustrate and analyze the simultaneous forces between two objects as represented in Newton's third law of motion using free body diagrams and in an experimental design scenario; and
Knowledge and Skills Statement
Science concepts. The student knows and applies the laws governing motion in a variety of situations.
Further Explanation
If object A and object B interact or collide, then object A will exert a force on object B, and object B will exert an equal force on object A, but in the opposite direction.
Though these forces are equal and opposite, the motion caused by them may not be. Students should draw free-body diagrams for each object involved in the interaction and then use the information derived to solve physics problems involving both objects.
A free-body diagram of a block resting on a rough inclined plane, with its weight (W), normal force (N), and friction (F) shown.
Supporting Information
Research
Smith, Trevor I., and Michael C. Wittmann. "Comparing Three Methods for Teaching Newton’s Third Law." Physical Review Special Topics: Physics Education Research 3, no. 2 (2007): 020105. https://doi.org/10.1103/PhysRevSTPER.3.020105
Summary: Our study examines three tutorials designed to improve student understanding of Newton’s third law: the University of Washington’s Tutorials in Introductory Physics TIP, the University of Maryland’s Activity-Based Tutorials ABT, and the Open Source Tutorials OST also developed at the University of Maryland. Each tutorial was designed with different goals and agendas, and each employs different methods to help students understand the physics. We find that students using the OST version of the tutorial perform better than students using either of the other two.
Research
Chen, Cheng, Lei Bao, Joseph C. Fritchman, and Hemin Ma. "Causal Reasoning in Understanding Newton’s Third Law." Physical Review Physics Education Research 17, no. 1 (2021): 010128. https://doi.org/10.1103/PhysRevPhysEducRes.17.010128
Summary: This study builds on existing work to investigate aspects of students’ causal reasoning in understanding Newton’s third law. Quantitative assessment is conducted to explicitly probe four attributes of causal reasoning, including the causal relation between a pair of interaction forces, magnitudes of interaction forces, the time order of interaction forces, and the action-reaction language. Detailed analysis of the findings and educational implications on assessment and instruction are discussed.