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Thinking about the purpose of an introductory physics course

July 10, 2017

I’ve spent some time this summer reading Improving How Universities Teach Science: Lessons from the Science Education Initiative, which is a great summary of the incredible work Carl Weimann and his team did to transform science education at the University of British Columbia and the University of Colorado.

The book is tells a detailed story of the efforts to bring about large scale change to the STEM departments of these universities, and doesn’t shy away from spelling out all the various pitfalls along the way. One of the most critical elements to their efforts were creating a set of learning goals for each course that are defined operationally in terms of what students will be able to do upon completion of the course. The book provides a wonderfully detailed guide on how to go about learning goals. To some extent, this is what we’ve been doing with standards based grading for a long time—we have a set of objectives for each of our units and assess students specifically on their mastery of these concepts. But we don’t really have any course level learning objectives for our courses, and so I’d like to use this post to explore some ideas around what course-level learning objectives for an intro course might look like.


We teach two flavors of first year physics, both of which use a modified form of modeling instruction. The honors physics course is taught to sophomores, and works students through the following sequence CVPM, BFPM, CAPM, UBFPM, MTM, PMPM, ETM, CFPM, MTET. The students in this class are adept at mathematics and sign up for the course to be challenged. Most students leave the course as very adept problem solvers capable of taking on challenging “goalless” problems that require them to synthesize multiple models. Student go on from this course to take Honors Chemistry, and then often our 2nd year physics course that uses Matter and Interactions. Though we haven’t explicitly written them out, I think I could easily come up with learning goals centered around problem solving, making simplifying assumptions and working with scientific arguments.

Our other first year physics course, Intro Physics, is a bit more of a challenge. This class is mostly taken by juniors and a few seniors, and almost all of them come from an Intro Chemistry course that follows the modeling chemistry curriculum. The students in this class are far less comfortable with mathematics, and don’t really see themselves as scientists. Students in this course usually go on to that Environmental Science, or occasionally our 2nd year Advanced Bio or Chemistry course. For some, it might be the only physics class they take in their lives.

Past approaches to the Intro Course

We’ve tried so many approaches to this course. Long ago, we taught from the Physics by Inquiry curriculum, and spent nearly 12 weeks on a deep dive into the properties of matter, beginning with devising an operational definition of mass using a pegboard balance, and culminating in a six page paper explaining why things sink or float (written around February). There were many parts of this curriculum that we loved—through experiment, students arrived at truly novel understandings and insights. But overall, the course was plodding to the point of being painfully slow for a majority of our students, and really we couldn’t justify a physics course that barely touched Newton’s laws in the spring.

Other things we’ve tried have included starting the year by challenging students to determine experimentally which has more energy—a battery or aue.

We’ve also tried working through modeling units on light and circuits, and while this has been enjoyable, I again this we’ve succumbed to the drag and experiment or discussion on for “just one more day” until many students were lost all interest in figuring out Snell’s law or the how the voltage of a battery affects the current through a resistor.

Most recently, we’ve moved to doing a “lite” version of Honors Physics, teaching most of the same models as our Honors Physics class, while removing a few ancillary topics and some of the more advanced problems. This seemed to be more successful—students in the class seemed to enjoy doing work similar to the work their peers in Honors Physics were doing. Also, every year we have a couple of students in Intro Physics who want to make the jump to our 2nd year Matter and Interactions course, and this certainly makes the transition easier for them.

Thoughts for this year

Though I think our current approach to Intro Physics is superior to many of our past approaches, I’m not sure that the ultimate goal/learning objectives for a good Intro Physics Course should be Honors Physics “lite.” It’s partly because I want to think deeper about our enduring understandings/course learning goals for the honors course, but if it’s true some of the students in our class are never going to study physics again, I feel a strong pull to expose them to more than just the 9 mechanics units we do with them.

I’m also deeply drawn to Project Based Learning, and have written about this a lot in the past:

There’s some particularly great discussion in the comments of the last two posts. But I still feel uncertain about making PBL more integral to my course for many of the concerns I raised before—I think just hard for students to achieve the same depth of understanding that they get from a lot of problem solving. Though that begs the question, should becoming adept at problem solving be a main goal of an intro physics course?

Ok, so where does this leave me? One other thing that has gotten me thinking a lot recently is Chad Orzel’s post, What Should Non-Scientists Learn From Physics. In this post, Chad gives his answer to what the essential understandings are for a “physics for non-majors course” which seems like a very similar audience to my Intro Physics course. Chad settles on two big ideas—one point of content—the atomic hypothesis, beautifully explained by Feynman here:

If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it) that all things are made of atoms—little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied.

Chad also offers one practice of physics—the idea that all of physics is built on approximate models and the power of simplification.

I really like this idea—the whole “assume a spherical cow” joke that summarizes the physicist’s world view so well. I think this idea really took hold for one of my second year physics students, who wrote me in a thank you letter:

I’ve loved learning to focus on a few fundamental ideas and model-centric thinking in order to feel confident in my ability to closely examine my world, draw useful results and tackle new and exciting problems.

This is awesome, but I know this particular student was exceptional, and she came to this understanding through a tremendous amount of hard work—she even went off and wrote a paper on her own to estimate what effect force of falling rain has on flying airplanes. She didn’t arrive at this idea from my preaching about models or fundamental principles, and a number of her classmates, even some who who are capable of solving the most challenging calculus based physics problems, still see physics as a enormous jumble of equations and arbitrary rules about when to use them. I also know from experience that this is the dominant way most of our intro students see the subject.

One possible start

Still, it’s a great goal to help students to have the ability to help students to see the power of highly simplified models, and I think the key is to make sure we are always helping students to see the model first and foremost, and assessing their ability to see and think about the approximations they are using, which naturally is one of the hardest things I know of to assess.

But here’s the start of a lesson that might open up the school year. Let’s just look at a bowling ball. Roll it past the students and have them make some observations. Very likely we’ll get answers that include “speeding up”, “slowing down” and maybe someone who’s willing to say “constant speed.” Then through a process of guided inquiry, we can can devise an experiment to help us to answer this question. We’ll need to put some limits on our observation—maybe we’ll observe the ball between two marks on the floor, and also decide what we need to measure, and how we will measure it. This will all take time—I’m imagining easily a class period for the first simple experiments where students are limited to just using a stopwatch, and likely more time when we go back with laser photogates or video analysis.

Eventually, I’m sure that we will all come to the agreement that over a few meters, the velocity of the ball is very nearly constant, and so a constant velocity model is going to be very useful. I think we can even then see how this simplified model makes it easy for us to make predictions—perhaps if I can borrow some bowling ball ramps from the local bowling alley so that we can have reproducible motion, we can predict when the ball will hit the wall on the opposite side of the classroom, and see that our model does a good job for answering this question. Then later, we can try to predict the time it takes to cross three baskeball courts in our field house, and see how the model breaks down as well.

I think there’s a kernel of something useful here, but I also worry that this falls prey to a lot of our previous teaching—going deep into something that can seem boring and lull students into not seeing the subtle details and insights that we are uncovering here.

But that’s what I’ve got at the moment. I’d love to hear thoughts you might have about what a successful intro physics course might look like.

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