A workable classroom taxonomy

A grid to aid preparing to teach

Building a workable account of doing physics through building models with which we can reason and represent might seem more like botany or a social science than physics. A useful output is a workable taxonomy: workable because it’s simple enough to be useable on the fly in the classroom. That means it'll probably not be comprehensive and incontestable: the taxonomy be a field guide, rather than a full and comprehensive account of doing physics. But that's not to say that it should not respect insights from the history and philosophy of physics, albeit re-wrought by didactical transposition.

Here is a simple grid, suitable for thinking about the range of models that might be simple enough to use in the classroom:

The key element is to recognise some of the common moves that you make in constructing models, and to represent these in ways that make their commonality evident across many topics. This is a part of the project of introducing children to the culture of physics, of thinking like a physicist, so that they can know what that is like: both the pleasures and pains.

Many of these moves will be in generating the enabling descriptions that allow the more formal models to get a grip on the world. These are often the difficult foothills, where the path is not clear, and many fall by the wayside. Careful route planning across this terrain, by well prepared guides, can engender sufficient confidence for repeat transits, necessarily associated with any effective problem-solving that involves modelling. So an effective approach to modelling starts a long time before writing the first (formal) model.

So what are these moves that we make, and how can we flag them up in ways that make the pervasiveness of the moves evident?

Noticing and recording are two groups of moves, but are perhaps too general as useful field guides. Although you might draw attention to the actions, after suitable priming.

What do we choose to notice here?

What will it be useful to record here? And why?

Noticing is a careful, but pre-physics-theoretic, activity, that results in qualitative or semi-quantitative results. So you can notice speeds and distances. You cannot notice accelerations, velocities, displacements (Forces could be either, depending where you are along the spectrum of refining the idea, because of their psychogenesis in human action).

Here is a workable framework:

In either case you can emphasise both selection and choice: depicting the lived-in world is a creative and purposeful activity. If there is a meta-message here, it's that the end goal, or purpose needs to be in view. You can guide children more easily, without many becoming dispirited in the foothills, if you share the reasons for the choice of path, and keep the end goal in sight, or at least in mind. It's an exercise in avoiding both Are we nearly there yet? and Why are we here?. Pacing and generating a sense of purpose and progress are all: this can, and probably should, be done with a light touch.

More granular moves are therefore easier to stage, as progress is visible. Here are a few suggestions.

We can imagine making progress in the construction of a model by one of only four kinds of moves, effecting:

For classroom use, you could translate these to a simpler language, or even represent the moves graphically:

The advantages of using a graphical language is that you can use it as a frame for the particular content, which is the approach taken in SPT. The focus can either be on the frame, or on the particular.

But the number of kinds of move, and the way these moves are represented, are choices for you to make. SPT gives one worked through example. What you should not do, I think, is leave the whole process of constructing models as an amorphous set of hidden moves, not explicitly identified and so made available for reflection. It's hard to see how a cultured view of a citizens education in thinking like a physicist could not contain these structuring elements. Tacit knowledge is not enough for a citizen's education in physics.