Teaching energy before forces improves outcomes for physics students
Most first-year college physics courses begin the same way: with kinematics and Newton’s laws. It’s a logical place to start; the topics are tangible, and the required math is relatively straightforward. However, that doesn’t mean it produces the best student outcomes.
In 2013 the University of Kansas (KU) began offering two versions of its introductory physics course. One continued using the traditional force-first curriculum; the other implemented a new energy-first approach that started with energy and conservation laws. The energy-first course more closely mirrors advanced courses, such as classical and quantum mechanics, that start with Lagrangians or Hamiltonians and use them to derive dynamics. Because the concepts of work and energy can be broadly applied—they underlie, for example, thermodynamics and quantum mechanics—students develop skills for solving a wide range of problems and recognizing commonalities between them. The new curriculum was developed to focus on those strengths. It also presents scalar quantities first instead of jumping right in with vectors, which students often find challenging. (For a reflection on the issues with force-first instruction, see the article by Frank Wilczek, Physics Today, October 2004, page 11 .)
Sarah LeGresley, Christopher Fischer, and coworkers at KU have now analyzed how the different courses affect student outcomes. They used two metrics to measure student learning: the Force Concept Inventory (FCI) exam, which tests conceptual knowledge, and performance in subsequent classes with introductory physics as a prerequisite, which was a proxy for quantitative skills and retention. Students who had energy-first instruction showed greater FCI score improvement than those in the force-first class. As seen in the graph, the benefit of an energy-first approach was greatest for students who had lower ACT math scores in high school.
The researchers also saw improved performance for the energy-first students in their downstream engineering courses. They attributed the improvement to increased fluency with not only physical concepts but also mathematical skills, because the energy-first curriculum relies more heavily on calculus. The study’s results suggest that energy-first instruction can help students both improve their conceptual understanding of physics topics and bridge the gap between physics and math. (S. E. LeGresley et al., Phys. Rev. Phys. Educ. Res. 15, 020126, 2019 ; thumbnail photo credit: Wikimedia Commons/User:Steevven1)