Month: June 2014

Energy Theater

At the summer Modeling Instruction workshops in Columbus, we are often lucky to have prominent physics education researchers visit us and speak to our workshop participants. On Wednesday, Dr. Stamatis Vokos of Seattle Pacific University joined us and he completely owned the crowd. I might be a bit biased, as I was really jazzed about his presentation of the Energy Theater.

Using work done by the Energy Project, a research group focused on discovering best practices regarding the teaching of energy in science, Dr. Vokos shared with us a new way to think about energy transfers and transformations. Dubbed the Energy Theater, this representation allows the students to act out the energy transformations and transfers in a system with each student representing a single unit of energy. There is an article in the May 2014 issue of The Physics Teacher that gives a good overview and provides an in-depth look at how to use the Energy Theater in the classroom. I’m only going to share our experiences, so be sure to check out the article.

As it was shared with us, there are four rules to the Energy Theater.

  1. Each student represents a single unit of energy.
  2. Objects correspond to areas that have been marked off on the floor (likely by tape).
  3. Each student represents their form of energy with hand signs.
  4. As energy transfers and transforms among objects, students move to different areas of the floor and change their hand signs.

We were given the example of a cup resting on a hand. The cup is being raised at a constant speed. We chose the person, surrounding air and the cup to be the system. In a modeling classroom, we have tools like energy pie graphs or bar charts that would let us model the problem like this:

piecharts

The great thing about energy pie graphs and bar charts is that they let students show how the types of energy present in a system are transforming from moment to moment. However, they don’t really let students consider how the energy is transferring between parts of the system. For instance, where is that thermal energy? Is it in the cup? The person?

Using the Energy Theater, our group identified the objects in our system and marked off areas on the ground to represent them. We did our work outside, so we used the blocks of concrete and split them up as shown below.

Screen Shot 2014-06-12 at 7.16.41 PM

Next, we decided as a group on hand signs to represent each energy type. While you can use simple hand signals, I wanted signs that involved more of our body to make them obvious. We came up with the following:

  • Kinetic – a simple sideways-V formed by spreading the index and middle fingers
  • Gravitational Potential – both hands on our head
  • Thermal – fanning our faces
  • Chemical – both hands on our belly

This is where the physics comes in. We had to work out as a group how many units of energy were in each object AND in each form. Our location reveals where the energy is while our hand signal reveals what form the unit of energy has taken. We had to reason out how the units of energy should move within the system and how they should change as they did so. The result is a glorious ballet of physics teachers having way too much fun.

As you can see, we (as students) really needed to think through how the energy transformations of the very simple act of a cup being raised at constant velocity. How much thermal energy is in the body? How much transfers to the air? Do we ever run out of chemical energy?

As we concluded our work on that problem, Dr. Vokos asked us to try the case where the cup is being lowered. At first, this seems like a simple reversal of the previous Energy Theater. We quickly realized though that things were different.

See how much fun you can have at a Modeling Workshop?

Reasons I Like This

  • Energy transfers are explicit. Students sometimes have trouble connecting the states of a system. While the O of the LOL charts (a.k.a. energy bar charts) can show energy moving into or out of the system, it doesn’t allow students to show how energy moves within the system.
  • It’s another representation to add to the energy model. Modeling is about finding multiple, consistent ways to represent the same phenomenon and this leads to better learning.
  • This feels like the “Walking Out a Motion Graph” activity in which students model a position or velocity vs. time graph using their own bodies and a motion detector. I like those active representations.
  • It is scalable. If you don’t have room, students can draw the areas for objects on a whiteboard and move multi-sided blocks from area to area. Think of a six-sided die with the faces each representing a type of energy. Check out the Physics Teacher article for a good picture of this.
  • It fits well with pie graphs and bar charts. At any moment, the number of blocks of energy and their types can be determined, so the rest of the class could construct pie graphs and bar charts as students perform the Energy Theater. You could even create a stop-motion Energy Theater.
  • Thermal energy transformations become very apparent here. We quickly realized how much of the energy being used must be transforming into thermal energy.

Concerns

  • Energy as a substance. According to Dr. Vokos, this representation requires students to think of energy as “an immaterial substance”. This makes me uneasy. Will this confuse students? Energy isn’t a substance, but then again, forces aren’t arrows. And we already represent energy as blocks in energy bar graphs. Is it okay to use this model to help them understand energy transfers?
  • Tracking of info. With so many people moving and switching hand signs, it will be hard for students to track all changes at once while the Energy Theater is occurring. I think this can be alleviated by filming it for review or moving through it multiple times and stopping the performers at key moments to assess the current state of the system.
  • Disengaged students. Notice the guy in the green shirt in the videos (me). I picked a role that required me to do very little. In the first video, I chose to be a unit of kinetic energy in the cup which never changes. In the second case, I was a unit of chemical energy in the body that never transformed. In both cases, I was assigned my role and then could have chosen to ignore everyone else. Yes, this is more of a classroom management issue, but with so many students at once, I’ll need to keep an eye on it.
  • The gravitational field. Since using the modeling materials, I’ve taken to explaining that gravitational potential energy does not reside in the cup, but in the cup-Earth system. My students quickly take to this and it sets them up well for AP physics when we discuss conservative forces and fields. How to represent this cup-Earth system in the Energy Theater? Perhaps breaking one area into two smaller ones? Dr. Vokos was kind enough to speak with me at length about this. His suggestion was to place the energy in the cup initially. Use that as your first model. Next, change the mass of the cup. Make it more and more massive and look at how the Energy Theater changes. What would happen if the cup were as big as the Earth? In other words, use the Energy Theater to build towards a revision to your model of gravitational potential energy that requires this new cup-Earth thing to be included. Ultimately, you could even move towards including the field.

There are numerous extensions to this activity. A teacher could easily assign new and different situations for students to investigate or slightly alter the existing state of the system. You might make stop motion videos of the Energy Theater alongside energy bar graphs. This new representation for energy transformations and transfers had me really excited, but I want to think this through before I bring it into my classroom. If you have thoughts of your own about this, I’d love to hear them.