Introductory Physics for Life Sciences

Memorization in Physics

I just finished my unit on circuits in Physics 132 and, along the way, discovered a useful tool for helping biology students grasp the importance of completely understanding and memorizing a mechanism.

In physics, we often consider memorization to be a “dirty word.” We pride ourselves on being the discipline that doesn’t require much, if any, memorization. In fact, many physics instructors I know will say, “I don’t want them to memorize.” We provide equation sheets and other memory aids in many physics exams. Usually, this aversion to memorization comes from a reasonable place: I think the aversion to memorization ultimately comes from the idea that we don’t want students’ inability to recall certain facts to get in the way of the problem-solving skills we actually care about.

However, I’ve come to the conclusion over the last couple of years that this disciplinary cultural aversion to memorization has perhaps gone a bit too far. There are certain facts that you do just need to know in order to solve problems. Many points in the literature emphasize the importance of teaching and mastering conceptual understanding upstream of the problem-solving process. This is the entire motivation behind Eric Mazur’s introductory physics textbook and the main takeaway from Paul and Webb’s paper, which advocates the same approach.

If we therefore accept that conceptual understanding is foundational to problem-solving success in physics, then it follows that students must actually remember certain fundamental physical facts. This is relevant in my circuits unit, where I continue to use a series of questions I developed 15 years ago involving the physical processes involved in charging capacitors: consider the voltage drops along wires (you can’t consider wires to be ideal, resistance-less conductors for this exercise), how those voltage changes can also be viewed as electric fields, and how those electric fields exert forces on the charges already present in the metal thereby charges the capacitor.

While teaching this sequence this past semester, I had a sudden inspiration in class, which I acted on. I told the students, after we had completed the sequence, that this series of questions and the underlying logic therein was effectively the “Krebs cycle for capacitors,” and that they really needed to know these steps.

Using the phrase “Krebs cycle” truly seemed to resonate with the students. I saw many nods of understanding that I had not seen before, nods indicating that they understood the importance of memorizing the sequence. Moreover, there was a slight giggle in the room, so I asked, “Y’all just surprised that a physics instructor knows the Krebs cycle?” Several of them said yes. I think that this reference to a fundamental biological mechanism served multiple purposes in promoting authenticity. I used the language of biology to emphasize that we were talking about a mechanistic process similar to the ones with which they are familiar and have experience memorizing. Moreover, the Krebs cycle is foundational, and so calling the series of physics steps that underpin capacitor charging a “Krebs cycle” showed the students, in a biologically authentic way, the importance of what we had just discussed.

Now, of course, I don’t yet know the effects of this reference, but I’ll be watching in office hours over the coming weeks to see the number of questions coming in about the capacitor-charging process. Unfortunately, I don’t have a lot of notes with which to compare from prior years, but often this process results in a lot of questions during office hours. If most students now seem to have grasped the process, I will consider it a beneficial step. Even if there’s no change, the use of a biologically authentic phrase such as “Krebs cycle” is, I think, a useful tool when teaching introductory physics for life sciences.

Some random thoughts on 131: a new way to look at math

While I am not currently in the rotation to teach 131, and probably will not be for some time, I still sometimes think about it. Frankly, it is nice to be able to just think without the pressure of having to teach it as the lack of pressure allows my mind to wander on the big-picture parts of courses in fun and surprising ways.

Last night my mind was wandering on 131 and I realized that there is another theme running through the course that I had not really made explicit to myself before: a new way to look at math. As you can see from the description of 131, the course braids several different threads. One of these is my general interest in the difference between math-in-physics and math-in-math (see the right column of the poster!). Another is the integration of computation. The insight from last night is that these, along with graphical analysis, are all aspects of the same goal: learning to use math differently than students are accustomed from their math classes.

Writing equations corresponding to models of nature.
Reading an equation to predict how systems will behave with changes of variables.
Using equations (particularly differential equations) as “stepping rules.”
Graphs as a mathematical representation.

While this is a neat insight, I am now concerned if there is too much in the class.

These are thoughts to keep pondering!

Perceptions of interdisciplinary critical thinking among biology and physics undergraduates – Review and thoughts

This is a collection of my thoughts from reading:

A. B. Heim, G. Lawrence, R. Agarwal, M. K. Smith, and N. G. Holmes, Perceptions of interdisciplinary critical thinking among biology and physics undergraduates, Phys. Rev. Phys. Educ. Res. 21, 010138 (2025).

The paper is available on the PaperCast at https://open.spotify.com/episode/394yVw46zKSA8gPYLKLaGh?si=7bb3c2173d9545aa

Structure

This post is a series of thoughts on different topics that arose as I read the paper.

Tasks as the basis of research as well as curricular design and sharing

Listening to this paper on interdisciplinary curricular design, one justification they mention for focusing on learning tasks is that tasks are a manageable level for curricular design research. Tasks are simpler than entire courses, and once designed, they can be sequenced into a full course. An additional argument is that approaching a course holistically is simply too complex. While I agree that designing a course by first defining overarching goals and objectives, then breaking those down by unit, and only then developing tasks to meet the established goals, is more complex, I believe it produces a much stronger result. My initial experience designing 131 is an example wherein I designed tasks first and then strung them together did not produce an effective course. Thus, while I recognize the value of research on tasks and understand why they serve as a convenient focal point for curricular design research, I struggle with the idea that tasks should be the starting point. This perspective connects with ideas I’ve been developing for my new graduate TA training system. Graduate TAs often focus on designing lectures and other tasks, but I want to encourage a more holistic perspective—thinking critically about course goals and objectives first. In summary, while I agree that tasks are a critical part of curricular design and a convenient unit of research, I do not believe they are an appropriate starting point. That approach feels backward to me. It’s like designing the perfect brick before knowing what you’re going to build. If you’re building a house, that brick might be useful. But if you’re building a boat, that perfect brick may not help—and trying to use it could result in a boat made of bricks, which is ineffective at best.

Physics education, especially for biology students and even engineers, is at a point where curriculum reconsideration may not be absolutely necessary, but is certainly warranted. We need to ask: what are we teaching, and why? This line of thinking is influenced by the Hake paper¹, which emphasizes that active learning is where learning happens. However, active learning takes time. This means that designing a course requires hard decisions: what do you teach, and—more importantly—what do you drop? I would encourage others, as Redish² does in his reconsideration of introductory physics for biologists, to start by digging into what you want students to learn and why—then move on to the tasks.

The “Earthworm Problem” as a Level-2 Problem

This is referring to

Alice Churukian, David Smith, Colin Wallace, Duane Deardorff, Daniel Young, and Laurie McNeil, Living Physics Portal: PALS Breathing Worms, https://www.livingphysicsportal.org/details/d7a0eea7-e6a5-4fb9-a644-c276ee0968bf.

Later in the same paper, they discuss the Nexus Physics curriculum’s well-known earthworm problem. This involves comparing oxygen absorption through the skin with oxygen usage in the body—a scaling law problem. Surface area scales with R², and volume with R³. For cylinders, surface area scales linearly with radius, and volume (or cross-sectional area) scales with R². This relationship is relevant here.

While the problem is solid in concept, I still find it somewhat lacking. Perhaps not inauthentic, but not as engaging as it could be. The main issue is that students are told exactly what to do: create this equation, graph that one, identify where the lines intersect. While this applies physics problem-solving techniques to a biological context—which the paper classifies as “level two”—I don’t like that the path is laid out so explicitly.

In my IPLS course, I want students to figure out how to approach problems. They may need some guidance, but ultimately, I want them to be able to look at a biological or chemical situation and apply physics tools independently. The goal is for them to encounter something in a biology or chemistry course and think, “I’ve seen something like this before in physics. I know how to use physics to better understand this phenomenon.”

Importantly, I want them to apply this reasoning to new contexts—not just replicate what we’ve done in class. That’s why my exams use novel scenarios. If they can look at something like bird vs. bumblebee flight and think about the role of Reynolds number, or apply physics when studying blood flow in chemistry or biology, then they’re doing what I hope they’ll do. If an instructor mentions the electrical properties of blood, they should be able to draw on physics problem-solving to deepen their understanding—not just memorize the concept.

So, while the earthworm problem has value, I believe it would be stronger as a more open-ended task. For example: “Why do earthworms have limited cross-sectional area per unit length?” Something that invites critical thinking, not just procedural execution.

Presumed Uniformity of Introductory Biology Curricula

I also want to mention another critique of the paper: its assumption about the universality of biology curricula. In adapting Nexus materials at UMass Amherst, I’ve found that our students arrive in IPLS with different backgrounds than those at the University of Maryland. This makes me wonder whether biology curricula vary more than physics curricula across the country.

My conversations with biology colleagues suggest that variation exists even within UMass. For example, Laura Francis emphasizes a mechanistic and quantitative approach, while Caleb Rounds focuses on data literacy and graph interpretation. Others still follow a more traditional memorization-based approach. These differences suggest limitations in the universal applicability of the paper’s ideas.

For this reason, I believe authentic IPLS development requires close collaboration with local biology and chemistry faculty. These partnerships help align course design with the actual experiences of students. A good example is how my focus on HOMO-LUMO transitions in organic chemistry—used to motivate quantum mechanics—emerged from conversations with Laura. Using shared language and figures, and teaching this content simultaneously in chemistry and physics, reinforces its authenticity for students.

In short, one must be cautious when trying to generalize IPLS implementations from one institution to another. Biology prerequisites and emphasis vary, and effective course design must reflect this.

The Importance of Language in Problem Authorship

Another interesting example from the paper involves two different prompts for protein unfolding. The first is essentially a physics problem imposed on a biological context—no more authentic than a cheetah chasing an antelope. While it might be fun, it doesn’t feel authentic to many students, and in my experience, some even resent such forced pairings.

The second prompt, involving the energy landscape, feels much more authentic. In addition to structural differences, a key factor is the use of biologically native language. This aligns with ideas from my mutual mentoring work: authenticity is enhanced when you speak the language of the students.

This is something that I find missing in many IPLS discussions. Language and conventions matter. For example, I used to describe HOMO-LUMO transitions as “excitation from ground to first excited state”—the physicist’s language. Calling it a HOMO-LUMO transition, though, immediately felt more authentic to students. I don’t have hard data to support this, but my classroom experience strongly suggests it helps.

The Value of Level-One Tasks

One final point: what the paper calls “level one” tasks can actually be counterproductive. Many students are perceptive. They recognize when a problem is a forced attempt to make physics seem relevant. When it feels fake, they may conclude that physics has nothing to offer biology. In fact, the paper eventually makes this same point.

What I’ve found effective are tasks where students can draw relevant biological, chemical, or medical conclusions. For example, calculating eyeglass prescriptions based on eyeball size, predicting absorption lines of organic molecules, or solving for a 70 mV membrane potential. These are meaningful, relevant facts, but students often don’t know their origins. When they see physics helping them understand such concepts, engagement increases.

R. R. Hake, Interactive-engagement versus traditional methods: A six-thousand-student survey of mechanics test data for introductory physics courses, American Journal of Physics 66, 64 (1998). ↩︎
E. F. Redish et al., NEXUS/Physics: An interdisciplinary repurposing of physics for biologists, American Journal of Physics 82, 368 (2014). ↩︎

Incorporating Student Choice into IPLS

Listening to the most recent paper-cast episode on student choice has given me some good ideas. This paper makes a very good case for providing students with choices of additional work beyond that which is mandatory. One way this could be done in 131 and 132 is by allowing for the option of Perusall comments within the textbook. This would allow students to opt in to the Perusall, an assignment which I believe to be valuable, but has traditionally been divisive. Perhaps that would encourage more detailed reading along with the homework.

Another idea would be for students to turn in additional practice problems. Many students request that I collect the additional practice problems for a grade. I have traditionally not done as an acknowledgement of the amount of work required for preparation in these flipped courses. However, if students can opt in to that assignment, then my concern is rendered moot.

Of course we wouldn’t be able to grade all of the problems. However we might be able to do a grade a subset or allow students to you know choose to turn in a certain number and we will grade a subset of that or some combination. For example we could require students to turn in a total of 10 problems with you know at least two from each worksheet by the end of the unit we would then grade five of these 10 on a 0-1-2-3 type scale.

In terms of the overall course grade distribution, we currently have a small percentage dedicated to the metacognitive journals which I also believe to be valuable but are, again, divisive. Some students find them quite valuable, but others see it as busy work. I suspect this is mostly a reflection of the amount of time students’ spend on it. However, I could make that percentage a student choice: they could choose for that portion of the grade to be one of these assignments. Perhaps even allowing for some switching over the course of the semester on a unit-by-unit basis. Students would then have the option of choosing an activity that best supports their learning, or they could choose to do none of these activities and have that additional portion of the grade just be reallocated to the standard preparatory homework or something to that effect.

Thoughts on “Using Framing as a Lens to Understand Context Effects on Expert Reasoning”

After listening to this paper, a few things are interesting right out of the gate:

The resource model of cognition hasn’t really propagated to biology yet.
Two they point out that experts have learned to reason across disciplines using cross-cutting concepts. Could it possibly be that experts have gained this ability because they were exposed to it in different contexts? I don’t think this is true but it’s worth thinking about the fact that it could possibly be.
I like the idea of engineers as existing in the middle of the idealized/real-example continuum with physics on the idealized end and biology on the other.