Engineering is not Physics

So, my three Intro Physics classes (9th grade) engineered some bumpers this week. This was their first attempt. I’m adapting a curriculum module from PASCO (“Collisions: Problem-Based Learning Module”), trying to mesh that with my momentum unit adapted from the modeling curriculum.

The first class to get to this initial build was a mess. I had them trying to document their design, with a bit of reasoning behind their ideas, and also build. That was too much for one block. Students lacked the time to do everything, and many ended up not working productively at all.

The other two classes I slowed down, having them draw and justify their designs one block (along with some other brief work on momentum). Then the next block they did the build-and-test. Both days, they worked with much more care and focus than the first group.

Not surprising: “make haste slowly” often applies to teaching. In this instance, I’m doing something new. I’ve had plenty of building projects in my classes before, but this time I’m aiming at something closer to engineering. Not being an engineer, I have only a dim notion of the process, probably not more than a caricature. But I know it’s more than just build something and try it.

Allowing more time is important not just because this is a new thing for me. Beyond that, I think engineering itself requires the students to take time to do things I had not considered: sketch, compare ideas, tie those ideas to physical concepts and experiences they’ve shared, learn the properties of the actual materials (e.g. how sticky is the clay?), get over the “failures,” reflect on what happened…. It’s good stuff and worth the time. And by this point in my career, I certainly can teach the physics efficiently enough to make room for engineering as well.


K*, our physics teacher intern from last year, recently shared resources with me. She’s helping plan lessons for the junior/senior advisory at her new school, on the subject of the gender/minority gap in the sciences. (Those resources, and others, are included below.)

I wrote back, and decided to include colleagues at my school. Then figured I’d post it as a blog, so here goes.

Hi Kate,

Thanks for these resources! Haven’t listened to the storycollider podcast, but the Renee Hlozek story was interesting to follow at the time. The “unit buddies” [described below] pulls me two ways. I love history, and putting student names next to famous ones appeals to me (“yeah, you may not know, but I’m a close, personal buddy of James Joule.”) At the same time, elevating the dead white guys makes me more uncomfortable every year**.

Some shifts took place at the AAPT meeting in July around under-represented groups in physics. A bunch of us noticed a reframing of the issue. Many efforts have concentrated on encouraging and supporting folks to go into STEM. That’s not bad, and it’s a way we HS teachers can contribute. But instead of trying to fix some supposed deficit that these students have, people were talking about fixing the culture to welcome them. As Frank Noschese put it: don’t build people a ladder if it’s just going to take them to a toxic environment. [twitter link]

Hard to change a culture, of course. Yet a buzz was going around AAPT, and I hear that perhaps The Physics Teacher will start addressing the matter directly. So I have hopes the community is starting to get it.

And… that’s what I wanted to put out there. While not wanting to make light of the subject at hand, I’ll conclude with an illustration using pop culture references:

The scientific community needs to be less like Rex Harrison singing “A Hymn to Him”…

… and, perhaps, more like the “Large Hadron Rap.”

In sum: Don’t be a friggin’ Higgins while you’re looking for a Higgs.

Resources K shared:

Some additional resources I’ve noted:

  • “Unheard Voices” Educator Resource Guides: New Link From the “Multiverse” website, goal: “Increasing diversity in Earth and Space Science through Multicultural Education.”
  • “The Social‐Belonging Intervention: Getting the Message Right” New Link By Greg Walton. Online supplement to “Psychological insights for improved physics teaching” in Physics Today last year (also worth reading).
  • I’m disappointed that the “This is What a Scientist Looks Like” tumblr (New Link) seems to have lost steam. But browsing that and reflecting might be worthwhile for us and for students.

*Haven’t checked with K about posting, so just giving the one letter.

**Even though I will become one ultimately.


Well, this blogging thing isn’t working for me. Or, I’m not working on this blogging thing.

But, Andy Rundquist has proposed this National Blog Comment Month task, which he mushes into the “NaBloCoMo” of my title.

That sounds challenging for me, and I’m going to give this a try. Wish me luck.

Once again, students have signed up to take a semester of astronomy with me as their teacher. For several years, I’ve started with a list of things I hope to pass along to the students. Listing these objectives challenges me to include the breadth of a general interest astronomy class while keeping the list concise and manageable. In the end, I always include more than we can get to in our single semester.

Seems like a good idea to put my latest version out in the world, maybe get some feedback:

Astro Learning Outcomes 14-15
(Sorry that the document must be downloaded. I haven’t figured out how to display the document in the post.)

I’ve toyed with adding some kind of learning objective: work done outside of class, reflecting, re-assessing… but it feels like that’s just looking for a stick with which to hit a certain kind of student. If I can hold kids accountable for all the standards I’ve already got on the list, do I really need to assess them on their homework and such? I’m thinking no.

A few years back, I tracked the forecasts from the National Weather Service, and compared them to the actual weather. By “weather,” I mean just temperatures and precipitation forecasts. The result was a spreadsheet.


I won’t bother going into observations about the data, and inferences about weather and forecasting. My main point here is that it seems like a worthwhile data-rich exploration for students. Figuring out how to arrange the data was itself in interesting exercise, even before attempting to note patterns and draw inferences from it. Seeing how the predicted probability of precipitation works out in practice is illuminating.

Because weather is of daily interest, I find myself recalling the exercise from time to time. I imagine that others would as well. So I think I’ll suggest this to one of our middle school earth science teachers.

“Why are you spending so much time on kinematics?” asks Dean Baird in his blog this morning, in the context of the Next Generation Science Standards (NGSS).

I’m not going to defend spending six weeks teaching quadratic equations, which is the position that Dean criticizes in his post. Years ago, I did that, but I’ve moved on. I do still teach kinematics, however, and now I want to clarify what aspect of kinematics I find it important to teach.

As Dean points out, the NGSS starts off with Newton’s Second Law: F = m a. Great choice. There’s a huge amount of physics in that formula: mass (not weight!) and the concept of inertia; force, including net force and vectors; and acceleration, which is not the same as velocity.

And that last point brings us to kinematics. Keep in mind that kinematics is not merely calculation and the use of formulas. Kinematics is the precise description of motion, and that includes important concepts and vocabulary.

In my class, the culmination of kinematics is not “solve this polynomial for a (or x, or t…).” My goal is for students to recognize the difference between acceleration and velocity. (For context, know that I teach a physics first course to ninth graders, in a state with a mandated subject-area test at the end of the year.) Yes, they do some algebra and learn to calculate an acceleration. We also use graphs, tables, motion maps, verbal descriptions, all that multiple representation stuff. And in the end, my standard for them is to determine whether an object is accelerating or not based on a given representation: Does this graph show an accelerating motion? Why or why not? How about this motion map? What about this diagram of an orbiting planet? This sentence describing a bike ride? And so on.

Recognizing acceleration is not easy. Most people don’t even perceive acceleration as they look at it. Drop a ball in class, ask the students if the speed is constant or changing, and many say the speed is the same whether the ball has fallen one centimeter or one meter. Check out Derek Muller’s video, “Can You Perceive Acceleration?” for a demonstration.

And that’s the problem with superficial coverage of kinematics. Without it, people conflate the notions of velocity and acceleration, and steadfastly maintain the Aristotelian position that all objects in motion have a net force acting upon them. Students even claim that F = ma supports them: “It’s moving, so a is not zero, therefore F is not zero”). Learning kinematics, specifically the conceptual understanding of acceleration, before Newton’s second law heads off that misconception. I push my students hard to see that distinction.

Teaching the concept of acceleration takes time and persistence, however. This difficulty makes me uneasy about the NGSS’s silence on the subject of kinematics. The standards take the concept of acceleration for granted, and I am concerned that the writers of assessments and the teachers of students will also neglect this fundamental idea. As written, the standard is about the mathematical relationship F = m a, and no understanding of the underlying meaning of the variables is necessary.

I’m not saying we have to start our year with kinematics. I’ve use several sequences: kinematics first, statics first, waves first, ray optics first… with good results. Regardless, within a topic, I hold off from the algebra until the students have understood that quantities represented by the variables. That means learning the concepts of net force, mass, and, yes, acceleration before working with the formula F = m a.

Dean describes (traditional) kinematics as “applied mathematics,” and not a proper subject for a physics class. I agree with that, so I don’t teach it that way. But I do teach (nontraditional) kinematics, and I exhort all you physics teachers not to skimp on the precise description of motion. Bear down on the concept of acceleration and make sure the students get that idea. If they can’t accurately describe what acceleration is, then F = ma is simply pure, unapplied mathematics, and you’re not doing physics at all.

So that’s my thinking. How about you? Precisely what kinematics do you teach (if any), and why (or why not)?

Chances are, you’re not going to Mars either.

But the video linked here, you can see a view as if flying through a giant canyon on equatorial Mars. This is it folks, this is how we are going to experience Mars. Sure, we’ll eventually get 3D, virtual reality, but we’ll be experiencing it secondhand.

But go look at it, and have the experience that we can get. As you watch, remember computers processed the images, yet they did not create them. This is not CGI, this is not Hollywood, you are seeing the planet Mars! Those rust and grey colors, plateau and gully shapes, smooth and bouldery textures are real.

And while I thrill at the notion of seeing Mars from a bird’s-eye view, I have to think: this looks really ordinary. This looks like home.  Parts of Earth look a lot like this, from a scenic overlook or an airplane. And again I find that exciting: much of what happens on Mars is the same as what happens on Earth.

This reveals an aspect of astronomy that I find empowering. Places far removed from us in space and time are nevertheless linked. The same laws of physics apply, chemistry and geology work the same way. And that makes the greater universe knowable to us. Differences occur, in a profusion of various circumstances, so Mars is not the same world as Earth. Yet we humans can know these other worlds and comprehend them in much of their wondrous specificity and individual character.

So no, I will never set my boots on Martian rocks, or sift its red sand through my fingers, much as I would like to. Yet thanks to the efforts of the engineers and scientists who put these misions together, and all the peoples who support their work, we have an experience of an alien world: Mars.