I want to talk about a question that was brought up a few times at Table 6, largely by Visala, namely: does something sitting still have potential energy if it has the potential to be lifted (or moved, risen, etc.)? I think that this question has its roots both in how we define particular forms of energy and in how we, as scientists, label those forms. Let me first rewind back to an interaction I had with some in-service middle school teachers last summer.
I've mentioned that part of my interest in the Energy Project emerged while I developed and taught a physics workshop for in-service teachers (Mary Bridget Kustusch was a con-conspirator with me on that). During our discussions on the different forms of energy, I realized that the teachers were using the same words to talk about different things from the other instructors and I. specifically the word "potential." When discussing a bouncing ball, we realized that the teachers considered the ball to have potential energy even when it was sitting stationary on the floor, simply because it had the potential to be kicked. This was the same issue that Visala brought up today concerning waster on the ground. It is also the same issue that that came up in the Scherr et al. 2012 article when the students were discussing leaves blowing in the wind.
I suspect that this is related to the (awful) nomenclature that we use for that particular form of energy. indeed it makes perfect sense to say that a soccer ball has the potential to be kicked. I am reminded of a particular metaphor that Rachel used in a talk she gave at the 2010 PERC in which she described "potential energy" as the maximum capacity that an object could be filled with the energy substance. An object has the potential to be filled with energy.
It is too bad that we impose this word on students. Dan, today, asked if potential was real energy. It is curious, though, that while the teachers discussed many types of energy (sound, chemical, motion, light, thermal), I don't recall once hearing a teacher come up with "configurational energy," (I haven't seen the pictures of the whiteboards, so I could be wrong...). It seems that an object's position is a far less salient attribute with which to associate energy than motion or temperature, say. it will be interesting to follow this thread through the week.
I'm glad you posted on this because not all parts of this question made it onto the teachers' question board yesterday afternoon. This discussion starts in the field notes at line 249 when someone asks about the difference between potential and stored energy. They write down the question "What is potential energy", but then don't write down the later question "do we need to differentiate things that CAN be charged or wound up with the energy they HAVE when they get charged up or compressed." I hope they come back to this discussion!
ReplyDeleteIn our parallel universe Physical Sciences Partnership Summer Academy on the coast of Maine, we had a conversation about this very point today. According to some kids in Bob's class, there was ALWAYS potential energy to be found. Sound energy? Well, the speaker goes to 11. Kinetic energy? Well, you could always kick the soccer ball harder. In every case, the kids said you could have had MORE energy. To modify what Brandon says, an objects always has MORE potential to be filled with energy...
ReplyDeleteJust as an FYI: Brandon posted about this again in terms of gestures here: http://scherrenergyproject.blogspot.com/2012/06/ue1-how-to-gesture-potential-energy.html
ReplyDeleteAND this has been discussed more over the course of UE1. In the afternoon on Wednesday in the Whole Class Discussion, a long conversation occurred about potential energy.
Brandon - have you had a chance to look at that discussion in more detail? Is that what you are referring to in your gesture post (but that you didn't discuss in detail)? I am excited to hear what you think about that discussion as well! This has been fascinating!