physics

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.

Theory v. Experiment

Ah, it’s an age old debate in physics departments – theory or experiment? When I was in college, it became clear to me that you needed to stake your claim as either a theorist or an experimental physicist. While both camps utilize tools of the other, they clearly each have preferred means of investigating and learning about the world. Usually, we ask our students to engage in both activities equally. First, they write up the background in their lab report, then perform some experiment, and then draw conclusions. This week, I decided to purposefully split the class into these two camps, each utilizing only half of the tools they typically have at their disposal.

The problem at hand was a classic conservation of energy problem involving a pendulum released from a height equal to its length. The pendulum swings down, encounters a peg directly beneath its support point, and then swings in a smaller arc around this peg. There’s a nice visual here. The AP Physics Lab Guide calls this the Turning Point lab and asks how high the peg can be placed so that the rope remains taut as the object swings up and over the peg. My students had this as a homework problem, so they’d had a chance to familiarize themselves with it prior to class.

I started class by explaining the theory/experiment divide amongst physicists and then splitting them along those lines. The theory group was essentially limited by not being able to make measurements. Whiteboards, diagrams, and equations were their tools. They split into smaller work groups, each trying a different approach. As they became stuck, they consulted with one another and ultimately wound up working together on a large whiteboard at one end of the room, ending up with the following results:

The experimentalists were forced to rely only on measurements. Searching the room, they found materials to build a pendulum which they began to modify. First, they overcame the trouble with the pendulum running into the string by releasing it off center. They then requested my phone so that they could level all of the components. Each time I thought they were going to get caught by some bit of uncertainty, they found a way to minimize it. Their procedure amounted to finding a lower bound where the string was definitely taut and an upper bound where it wasn’t, and then narrowing that range with multiple measurements. They used the camera on my phone to record the swings so that they could review them. Here is the apparatus that they devised:

After each group had worked through their individual methods, I had them choose a spokesperson who then presented the group’s results to the class. I gave them instructions that if asked questions, they could (and should) share the load of answering them with their group members. I found that I was able to ask some pointed questions of the group that was listening as a means to keep them engaged and responsible for understanding the work of their classmates. At the end of it, the experimentalists determined that the location of the peg was 28.5 ± 0.5 cm as measured from the support pole while the theorists found that it should be placed at 3/5L, with L being the length of the pendulum. For this particular setup, that gave a result of 27.9 cm. Success!

Some thoughts on this activity

Pros

    It’s fun and a different way to approach a lab. Rather than reading through a bunch of identical lab reports myself, the class was able to quickly (2 periods for the entire process) develop an understanding of how to solve the problem in two different ways.
    I like that it put some focus back on good lab technique. This is an AP physics class and the folks that write the AP test have made a recent push to ask questions about experimental design. In the report out, students were able to probe sources of uncertainty in the experimental design and hear about different sources of uncertainty that they may not have considered if they had written their own report.
    The more I try pulling problems off of the page, the more I like doing it. If I can keep these to two periods, they would make a great way to really investigate some of the classic physics examples that we see in texts. These can become quick lab practicums and be graded or just done for the joy of learning. (I didn’t grade this.)
    The collaboration was great even with girls being pushed outside of their comfort zone. Given the choice, many of my girls would self select into the theory group, but this forced some of them to think about ideas and work on skills they might ignore if given the choice.

Cons

    Group size. I have my biggest class of AP physics ever this year at 13. With one student absent, I had two groups of six. And while everyone was engaged, I would want to shrink the groups to perhaps four. I’m not sure how well this would scale to a larger class of say 25 or 30. I think decreasing group size would also lead to more voices. In this instance, half the class already agreed with one another when it came time to present, so it was really only two voices that we needed to hear from.
    I’m a bit worried that not every problem will have the right blend of theory and experiment. This one seemed to work well as both groups were finishing around the same time. I’m not sure how many problems will strike that balance as well as this one seemed to. What do you do with half the class if they are done in 15 minutes?

I’m looking forward to giving this a try again when I find the right problem to investigate.

Physics + Comics = Feynman

I haven’t been posting for a while, in part because I’ve been really busy with work, but also because I’ve found myself frustrated a lot this year. This blog was never meant to be a place for me to vent, so I’ve avoided it while trying to work on my courses. I’ve missed it though. Writing here last summer was enjoyable and I want to do it again, so I’m easing back into blogging the way you ease into a hot bath – slowly but with a feeling of great pleasure.

Physics is one of my great loves, but nearly equal to it is my love of comics. Reading and collecting comics has been a lifelong hobby of mine and my current collection has grown to embarrassing proportions. Like many folks, my first exposure to the artform was the super-hero genre, and while it still remains a favorite, I quickly found that comics can tell amazing stories involving mystery, fantasy, history, horror or even work as non-fictional pieces. If you want to learn more about what comics can do, I recommend Scott McCloud’s Understanding Comics.

So why am I writing about comics on a physics and teaching blog? Recently, I finished reading a biographical work – Feynman by Jim Ottaviani and Leland Myrick and published through First Second Books.

If you’re familiar with Richard Feynman through his famous lectures or the many popular books written by him or about him, I recommend you pick up this graphic novel. Jim Ottaviani does his research well. He includes classic Feynman moments such as Feynman cracking safes at Los Alamos, the phone call he received from the Nobel committee and his testimony to Congress regarding the Challenger disaster. But the creators also include information straight from Caltech’s archives, such as a commencement address at Caltech and the QED lectures. A speech given at Far Rockaway High School, unknown to me prior to reading this, is a personal favorite. We also sit along side Feynman as he tells stories to his children and we’re at the bedside of his first wife Arline with him as she dies. Leland Myrick’s art work makes this such a heart breaking moment that we must bear witness to it, much as Feynman himself did. So many personal and public moments of this man’s life are crafted and presented with the utmost respect and admiration by the creators that you’ll feel like you were along for many of them.

What truly struck me about this work is its ability to embrace the philosophy of Richard Feynman in conveying his ideas and life. Feynman is known for approaching many ideas from a visual/pictorial point of view. He preferred to be able to visualize what he was learning and put off calculations until the thing was understood. Myrick uses this idea as shapes and symbols float through a panel in which Feynman is working out Platonic solids in school or as he develops his famous diagrams for QED. And at times, full panels are given over to diagrammatic analogies as the “voice” of Feynman narrates his thoughts. In this excerpt from the publisher, he explains nuclear fission to a room full of people as he seemingly manipulates the atomic particles. Of special note, nearly all of the Alix Mautner lectures he gave on QED are told this way with panels being filled with rotating arrows, path integrals and squiggly lines – just as Feynman himself understood these ideas. The importance of this type of understanding is stated so clearly by Feynman himself in an exchange with Freeman Dyson. As the two men relax in a rundown motel during their cross-country drive, Feynman, while talking about professional journals being filled with his “squiggles” says,

“Because you know, I dislike talk that says there’s no picture possible … that all we need to know is how to calculate something. The power of mathematics is terrifying … and too many physicists give up trying to understand their equations. Well, I want to understand them.”

This is something I struggle with teaching my students everyday, topic after topic, but I feel they are seduced by the apparent sophistication and surety of mathematics. I need to find a way to make that doodle or squiggle on the board carry just as much weight as the equation written next to it.

This graphic novel is a fantastic work and I’ll be sure to check out the other science related work by Ottaviani and Myrick.  If you’re interested in knowing Richard Feynman better or just meeting him for the first time, you should make time to read this comic.

A Work in Progress – My Teaching Philosophy

I’m mentoring a new teacher to our school this year and he recently asked me about my teaching philosophy. Our school’s website has these snazzy little bios about each of us that include a picture, contact info, a snippet from our teaching philosophy and a fun fact about ourselves. (Looking at mine, I really need to find something fun to do in my life.) In order to prep his, the teacher I’m mentoring hoped to read over mine to get an idea of what one should look like. And I’m afraid I may have failed him. My teaching philosophy is small and still a work in progress, so I’m not sure how helpful it was.

See, when I started teaching many moons ago, I didn’t know squat about instructional methods, pedagogy or assessment. So when writing my first teaching philosophy, I filled it with edujargon and things that I thought teachers were supposed to say. Looking back at it, I cringe and wonder why my current school ever decided to hire me. I’ll spare you from reading my thoughts on Socratic dialogue and “knowing your audience” (I can’t believe I wrote that). Hidden under all of that jargon though lurked a single thought about teaching that drove me. I think I was too embarrassed at first by its simplicity to share it, and once I ultimately chose to share it, I would downplay it by joking about it. Here was the sum total of my thoughts on teaching physics circa 2002-2007:

I love physics. I will do anything in my power to get more people to learn physics so that I have more people to talk to about physics.

That was it. I’m not sure how I used this to inform my classroom structure or grading scheme, but it was something I honestly felt. Looking at it now, the statement is incredibly self-centered which was probably reflective of the approach I took to teaching my classes at the time – me at the front of the room putting on a show. Thankfully, for my students, I’ve learned some since then.

A year ago, our head challenged us all to articulate our philosophy surrounding our practice and to reflect on it during some summer professional development work. Having taught using modeling instruction for two years and spent my first few months online reading teacher’s blogs, I took a stab at revising mine. It’s not much longer, but here, in unedited form, is what I came up with:

  • Science is something that must be done by students. Reading about it will not suffice. Science is an activity, not a topic. (Ex. Modeling Instruction)
  • Everybody can learn physics. Physics is often seen as the first gate class which admits smart kids but keeps dumb ones out. This is a damaging view to the students and the subject.
  • Students should always know exactly where they stand at all times. This requires timely, descriptive feedback that is not obfuscated by points. Additionally, they should know exactly what you want them to learn. (Ex. SBG grading)
  • It is my job to make my students realize that they don’t need me. They are capable of learning about the world around them and how it works on their own. (Ex. being less helpful, confidence)
  • Let students push beyond the bounds of your set goals and when they do, reward them.
  • Technology must be an appropriate part of the classroom, as it is a part of the students’ lives. (Ex. electronic book, LabPro and many more)

Obviously, it still needs some work. I’ve started to include examples of how I incorporate these ideas and you can clearly see the influence of some of the superheroes of the edublogoverse. I’m not entirely happy with the technology one, especially the examples, but I felt it was important to address it. Tech is not the answer to all of educations problems but it can be a powerful tool for learning at appropriate times. Additionally, I now note that there isn’t anything addressing gender or specifically teaching girls. I need to think about why I didn’t address that. Ultimately, each of the above ideas needs some expansion and discussion, but I wanted to get at the core thoughts I’d developed in recent years.

I shared the above with my mentee and I’m waiting to hear back from him. I’m eager to see what he comes up with as a new teacher more firmly entrenched in this new century and the current educational climate in the country. Until then, I’d love to see what others have written, so if you care to share yours, be sure to leave a link here.

My SBG Start

After spending the end of last year and most of the summer reading about standards based grading, I decided to jump on the SBG express. Like a travelin’ hobo with my bindle full of dreams of meaningful grades, I found a traveling companion (the other physics teacher in my department) and together we set off for the grading frontier. Our admin team was very supportive and they gave us plenty of freedom to develop the assessments that we feel will benefit our students learning. During the summer, we met to share our standards for our first units and to discuss any anticipated problems we felt might crop up.

School started two weeks ago, and we’ve both given our first assessment under SBG. Things have gone well (though I have yet to hand back the quiz), but I want to share a couple of the pitfalls we have encountered and how we’re choosing to deal with them.

Multiple grades for a single standard on one assessment.

Often, a quiz will contain multiple questions that address a single standard. Should we grade them all as a single attempt, average the scores together, or use the score on the last (i.e. most recent) problem? Maybe I should just write smaller assessments, but physics is such a cumulative science that standards are going to pop up over and over. I’ve decided to use all of the attempts on a single assessment in determining the score I report to the students. I think that gives them a more representative view of their current knowledge and avoids awarding coincidental correct answers.

General problem solving (arithmetic, algebra, units, sig figs, etc.)

So, what do you do with all of the math background skills that a student is supposed to be proficient in when they enter your physics class? Previously, I’d penalize a student 1/2 point for every missing unit or a careless algebra mistake. With SBG, I can’t in good conscience lower a student’s score on “Propagates error in sums/differences” when they forget to divide by 2π. Instead, I created a separate standard called “Practices good problem solving” which is my catch all standard for those math/technical skills needed to succeed in physics that I expect students to have when they enter the class. Additionally, if a student receives a low score in this, they still know what area to focus their efforts on.

The above is certainly not exhaustive and I imagine I’ll have more to share in the future. We’re still working out the translation of standards scores to percent/letter grades and how semester exams affect grades, but thus far, I think we are both happy with where this is leading.

My Favorite First Day

Today was the first day of school, so I’ve decided to make it my first day of blogging too. I want a place to reflect on what works and doesn’t work this year, since I’m trying a number of new things and continuing to tweak old ideas. I’m super excited about the changes I’m making to how I give students grades and feedback. Thankfully, I’m not alone. The other physics teacher and I are bringing standards-based grading to our courses this year. There are still some obstacles to overcome, but this is the first time I’ve been excited to assess students since becoming a teacher.

Tomorrow starts the scientific reasoning unit in my honors physics classes and I absolutely love this first week. It’s full of swinging pendula, vigorous student debate about confidence and uncertainty, failures, new knowledge and the idea that my students really don’t need me. With just their eyes, a meterstick, a stopwatch and a little math, they can tease out one of Nature’s secrets themselves. You know that scene in Willy Wonka and the Chocolate Factory where he reveals the chocolate room?

This first unit makes me feel like that.