Models of Potential Energy

I want to present some examples of some of the models of potential energy (or gravitational energy) which the teachers discussed as they gathered in the lobby to compare Energy Cube diagrams.

In particular, three separate models of potential energy emerged: potential energy as stored energy, potential energy as always present, and the standard model of potential energy is something that kinetic can turn into. I want to simply post some examples of these three models to spark discussion. The teachers spent roughly half an hour negotiating these different models, trying to either select one over another or create a hybrid of multiple models and these clips are taken from different portions of the conversation.

I should add that a fourth model, that an object has the potential to have energy, did arise, however Lezlie was quick to directly address this issue.

To add some context for this discussion as a whole, the groups had observed Lane fire a whirlybird earlier in the afternoon. The students were tasked with picking two (roughly) consecutive moments (e.g. beginning to pull the elastic band back and having pulled it all the way back) and using the energy cubes to track the energy flow.

Let me begin with the model of potential energy as stored energy. Here is a clip of Michelle*. [UE1 120628 1550 Front&Lobby Stored Energy]. This statement occured shortly after Lezlie explicitly distinguished potential energy from the "potential to have energy." (the original video is "UE1 120628 1537 Front&Lobby." the time stamps are for this video.)

[00:13:54] Michelle: I like the word "stored" 'cause the rubber band is stretcehd. To me it's storing energy that it's going to be able to use. The potential, it's like you're saying anything can have potential, you know, but if it's stored energy, like in a battery or in a stretched rubber band, that means you can use that storage, like in a hibernating bear or your pantry, or your- you can use that.

I think one of the most interesting parts of this clip is that Michelle explicitly distances her model from the word "potential" preferring the word "storage." I think that Michelle chosing a more suitable word for her idea as the teachers negotiate the meaning of potential energy conveys a depth to her understanding. It is notable, also, that her model is not limited to elastic energy, but contains a wide range of objects in which energy can be stored.

Let me move on to the second model of potential energy: It is always present and only take over once enough kinetic energy has been transfered elsewhere. I should note that this seems to recal the "impetus" model of forces, though I don't mean to imply any particular stance towards misconceptions (I suspect many of you can guess, though). Here is Theron explaining this model [UE1 120628 1601 Front&Lobby Potential Always there]:

[00:24:45] Theron: What I think was the- the- kinetic energy of the whirly bird rocket thing was transfered through friction to air molecuels around it, is what I had in my head. And then the gravitational energy was constantly there. And then eventually, it's- the potential is gonna pull it back down.

Although this model, at first listen, seems to conflate energy with force (or impetus), an important thing to notice is that Theron maintains conservation: the kinetic energy all transforms into thermal energy. The question, however, becomes how does potential energy relate to other forms of energy in this model.

Finally, let me present a brief clip of Doug presenting his model of potential energy as somethign that kinetic energy can transform into. This model is closest to our standard conceptual model of potential energy [UE1 120628 1600 Front&Lobby Standard Model]

[00:24:10] Doug: after the rubber band has stopped transfering energy, at that point it would have had its maximum kinetic energy. But as it's ascending, that kinetic energy is transforming into potential energy. Because you're- you're going higher but you're slowing down. The higher you go, the slower you're going, but hte more potential energy you have.

As a teacher, this particular clip makes me want to jump up and dance. From the researcher perspective, I think it's interesting that Doug incorporates two particular elements into this model: a height dependance and a gradual transformation from kinetic to potential.

So, these are the three basic models of potential energy that I observed durign this discussion. The teachers spend a good deal of time negotiating these models. I plan on examining this process in more depth over the next few days. Lane and Lezlie, for their part, largely let the teachers debate among themselves, generally only clarifying points that teachers were making. I recommend watching the whole episode, especially after the third group presents their diagram.
*please correct me if I used the wrong names.