In defense of Newton, but…

For the past 5 years, my students (mostly high school seniors) have spent the majority of the school year learning Newtonian Mechanics – a way of thinking about how things move and why they move that way. We’ve dabbled a little in other areas like light, sound, electricity, and magnetism…but most of the year has been devoted to mechanics.

There are legitimate criticisms of this approach:

Lack of exposure to modern topics. Lack of student choice in the curriculum. Some students lose interest. Little on the history or nature of science (something most K-12 science courses are slim on).

There are also benefits:

Robust, coherent, lasting understanding (Evidence: FCI). Greater likelihood of success in college science courses (Evidence: Success in Intro College Courses and FICSS). Understanding that can be used to problem-solve  (Evidence: FCI and MBT correlation)

Some general thoughts:

I would truly like to incorporate more modern topics. However, most modern topics make little sense without at least a semi-quantitative mathematical and graphical understanding of motion. At the very least, we should strive for this as part of the course. Also, motion must be related to the physical world. Some have tried calling motion a “math topic”. I suspect that this often neglects the development of these concepts in relation to reality and typically without careful operational definitions of concepts (position, velocity, time). As for forces, I could see them being treated more qualitatively, but again they must be developed, defined, related to real situations that we can observe with our senses, represented with multiple diagrams, and connected to students’ understanding of motion. Forces make little sense without understanding motion.

From my experience, Newtonian mechanics is going to take many first-year physics students at least half of a typical high school course to understand, remember, and be able to use the concepts. If our goal is for students to understand, remember, and be able to use Newtonian Mechanics, then we need to be willing to give them the time and pedagogy necessary to accomplish this. If our goal is exposure (some call it “Pseudoteaching“), then Newtonian Mechanics can be “covered” in a week.  I’m not saying that exposure is bad. Exposure to any physics concepts, whether Newtonian or Quantum Mechanics, is a good thing…but we have to know when we’re exposing students to ideas and when we’re helping them to understand, remember, and be able to use those ideas. There are days when I absolutely feel like cutting short Newtonian Mechanics, giving it the “one week” treatment, and jumping into modern topics with students. I still might one of these years. Priorities…

A couple of years ago at a modeling workshop, Mark Schober posed a question that I found to be a useful way to think about what we choose to teach. He asked…

“If you weren’t allowed to give the test until one year after the lesson/s…what would you teach and how would you teach it?”

“Newtonian mechanics” and Modeling Instruction  have been my answers to his question. BUT…I don’t think I’d answer the following question in exactly the same way…

“If you were trying to inspire students to continue studying physics either at college or independently after they leave your class…what would you teach and how would you teach it?”




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2 responses to “In defense of Newton, but…

  1. This is where I like Rhett’s comments in the Uncertain Dots episode about this ( He wants students to study something *on their own* in depth. I have my students do some lab design throughout the year, which culminates in using physics (primarily Newtonian mechanics) to explain a situation of their choosing as a final project (some use ‘capstone’). They dive in deep for 2 weeks to explain something they are interested in using the physics they have learned. And they love it. That, I think, can get many of them fired up about learning science despite ‘only’ learning mechanics.

  2. Sam

    I like the lab design idea. I’ve had students do independent research projects and they often have to fall back on their understanding of the basic mechanics models to answer their research question. Requiring them to do an experiment of some sort would strengthen the project. One of my favorites was a student who tried to answer this… “Could a 5oz swallow carry a 1 lb coconut?” from Monty Python. … Force diagrams were really helpful. I wonder whether it’s possible to start with these kinds of project ideas and then work through mechanics as needed. I’ve always had the student-driven research come near the end of mechanics.

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