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2012 May 29

Acronyms for physics modeling instruction

Filed under: home school — gasstationwithoutpumps @ 10:33
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In reading one of Kelly O’Shea’s posts, Extra Tests, Bundled Objectives, and Changes for Next Year, I was struck by the number of unexplained acronyms there were.  Looking through posts by other Modeling Instruction advocates, I noticed that they all used the same acronyms: the acronyms seem to be a standard part of the training in Modeling Instruction—a secret code that lets people know you are part of the fraternity (or sorority, in Kelly’s case). Do you have to learn the secret handshake as well?

I wonder how much the acronym shorthand helps the Modeling Instruction teachers talk to each other and how much of a barrier the arcane lore is for other teachers to pick up the methods of Modeling Instruction.  Do other physics teachers use these acronyms?

I attempted to translate the acronyms, based on the usage in Kelly’s post.  In a few cases, I had to go elsewhere to find other uses, as I couldn’t guess from just Kelly’s usage.

Constant Velocity Particle Model
Balanced Force Particle Model
Newton’s Third Law (or Newton’s Three Laws?)
Free Body Diagram
Constant Acceleration Particle Model
Unbalanced Force Particle Model
Momentum Model
Center of Mass Model
Projectile Motion Particle Model
Energy Transfer Model
Centripetal Force Particle Model (I guessed this wrong the first time—I thought the C was for “constant”.)
Uniform Circular Motion
Momentum and Energy Transfer (more commonly called “collisions”, I believe)

Elsewhere I’ve also seen

Conservation of Energy and Momentum
Conservation of Angular Momentum

Incidentally, the Matter and Interactions text, which is sometimes cited as ideal for Modeling Instruction of calculus-based physics, does not use these acronyms, preferring more English-like terms such as “Momentum Principle”.


  1. Hi there,

    The acronyms aren’t part of modeling instruction (MI). In fact, my names don’t always match the MI names. I wrote them out a lot in earlier posts, but it just became quite tedious to continue doing so, and I don’t really think of my blog as being read by a lot of people who wouldn’t know what I was talking about (though I guess I know better now!). Below, I’m going to give what I mean by each acronym:

    CVPM = Constant Velocity Particle Model, yep!

    BFPM = Balanced Forces Particle Model, yep!

    N3L = Newton’s Third Law. Not a model, but a handy way of writing it (along with N1L and N2L).

    FBD = Free Body Diagram, and I think this is pretty universal (I learned in in high school, and we definitely weren’t doing modeling!)

    CAPM = Constant Acceleration Particle Model, yep!

    UBFPM = Unbalanced Forces Particle Model, yep!

    MTM = Momentum Transfer Model

    COMM = the old name for MTM. It was Conservation of Momentum Model. Momentum Transfer is better, though.

    PMPM = Projectile Motion Particle Model, yep!

    ETM = Energy Transfer Model, yep!

    CFPM = Central Force Particle Model. I don’t use “centripetal” because it’s unnecessary vocabulary at that point in their physics learning career. Other people do use this same acronym to mean Constant Force Particle Model (which I don’t like at all, because it seems too limited).

    UCM = Uniform Circular Motion, and I think this (like FBD) is another really common one.

    MTET = Momentum and Energy Transfer. It’s not its own model, but is more of a second time through the conservation laws (plus solving multiple fundamental principle problems).

    COEM = the old name for ETM. This was Conservation of Energy Model. Energy Transfer is better, though.

    COAM = ? I’ve never seen this one before!

    A lot of these are my own shorthand (or shorthand that I picked up from Matt Greenwolfe). While it is obviously mainly shorthand for MI concepts, it’s not coming from the MI workshop, nor the official materials. I should definitely be a little more careful about making sure I define all of my acronyms somewhere, since I use them so freely. The kids use them, too, though I do check very often (verbally) to make sure that they know what the acronyms stand for. So far, so good. They always know what they are saying. :)

    I think the Bundled Objectives post is an unusual case, though, because it was assuming knowledge about the way I’ve been using objectives before (and I think all of those older posts spell out all of the models).

    Thanks for bringing this to my attention!


    Comment by Kelly O'Shea — 2012 May 29 @ 10:49 | Reply

    • I hope you’ll consider placing a “Glossary and Acronyms” link at the top of your page. I have a degree in physics and know the meaning of every term you mention yet wouldn’t have guessed what most of those acronyms stood for without a lot of head scratching. I haven’t been confused about the concept of conservation of momentum since high school, but call it “MTM” and, okay, now I’m lost.

      I’m not complaining about your use of new terms. Every new field, or new approach, needs new terms that are optimized for discussing their new ideas. Writing those terms out every time is annoying to both writers and frequent readers. I’d just like to suggest that you make it easy for new or infrequent readers without making it hard on yourself: include a link to an alphabetized glossary/acronym sheet.

      Comment by Glen — 2012 May 29 @ 17:32 | Reply

      • I have no intention of using these acronyms—I found them as mysterious as you did. I have no problem with writing out “constant velocity” or “momentum” when I need to refer to the concepts. I just was bemused by the very large number of them in one post, and a tendency for several of the physics teacher blogs I read to use these acronyms frequently without defining them.

        I used to be a computer engineer, and that field was full of acronyms that had a relatively short lifetime. Reading papers even 10 years old was often a struggle, because acronyms had already been recycled to have totally different meanings. Biology is as bad about creating acronyms and short names (the same gene may have 10 different names, because 10 different groups were studying it, and each name is a meaningless acronym).

        As a result of this experience, I rarely use acronyms when I can avoid it, and I try to use the unabbreviated form first. For example, I often work with Hidden Markov Models (HMMs), just as I used to work with Finite-State Automata (FSAs) and Very Large Scale Integration (VLSI).

        Comment by gasstationwithoutpumps — 2012 May 29 @ 17:47 | Reply

      • That’s a great idea. I’ll add it to my list for this summer. :)

        Comment by Kelly O'Shea — 2012 May 30 @ 02:20 | Reply

  2. I’ll second the fact that FBD, N2L, N3L, and UCM are in common usage outside of modeling. N1L not so much oddly enough.

    I’ll also agree with Kelly and say that few acronyms were part of Modeling Instruction. When I went through it (with Matt if I remember correctly) we tended just to use names.

    Comment by Dave — 2012 May 29 @ 12:14 | Reply

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