One thing that’s been on my mind is the extent to which our physics teaching majors are or are not developing identities as physicists/physics majors. Coupled with this issue of identity development is the concern that our physics teaching majors are not strongly integrated socially and academically with the rest of the physics majors.

There are a couple of factors driving this:

Physics teaching majors are not merely physics majors. They are also MTeach students. MTeach has a strong presence in their undergraduate trajectory. More specifically, students in a particular cohort are likely to take eight courses together to fulfill their minor in secondary education. MTeach has a very nice informal gathering space, where MTeach students hang out, get work done, etc. It’s a place where students are forging their sense of belonging in a community and developing identities as math and science teachers.

Most, but certainly not all of other physics majors, go through the calculus-based introductory physics sequence. In their sophomore year, most physics majors take a year of modern physics and a year of theoretical physics (i.e., math methods). So in the first two years of the program, a cohort of physics majors will have taken 6 physics courses together. Being in those courses and hanging out /working in the physics majors lounge working is partly where physics majors forge their sense of belonging to the community and develop identifies as physics majors / physicists.

Most of our physics teaching majors, however, are going through the algebra-based physics course, not the calculus-based course with the physics major cohort. For some, this is because they decide they want to pursue physics teaching only after taking our algebra-based physics course. For those who know early on they want to pursue physics teaching, it’s likely they don’t take the calculus-based course because they haven’t taken calculus yet, and are advised to take the algebra-based course. And while the graduate school track physics major concentrations require that students take the sophomore year theoretical physics course, physics teaching majors don’t have to take theoretical physics if they take both linear algebra and differential equations from the math department. So far, very few physics teaching majors take theoretical physics.

What does this mean for our physics teaching majors? In the first two years that our physics teaching majors are in the program, they take only two physics courses with other physics majors–the year of modern physics in their sophomore year. They don’t become integrated deeply at all into the a cohort of physics majors, because they weren’t in the same courses freshman year and then they don’t struggle through the very challenging calculus-based physics and theoretical physics course with the rest of the physics majors. Most of the physics majors go onto take a demanding course load in their junior and senior years, including a mix of required and elective courses, including some courses that verge on graduate level work like courses in quantum field theory, general relativity, etc. Physics teaching students take a few more required physics courses at the upper-level (e.g., thermodynamics), but they have less required physics content courses (in part) because they are required to take a sequence of physics teaching courses offered in the department. This is just to say that, even in their junior and senior years, physics teaching majors are unlikely to have social or academic interactions with the rest of the physics majors. And while they could elect to take more upper-level physics electives, they are not likely to, in part due to peer groups but also because many physics teaching majors are dual certifying in mathematics, so they are busy taking other content course in the math department and their education courses which required a lot of field experience time.

I’ve been thinking about this a lot recently, and then it really hit me hard last night when only one physics teaching major came to the annual physics department pot-luck / party / gathering. Not surprisingly, the one physics teaching major that came is quite socially integrated into the physics major cohort, chose to do research in physics not physics education, and elected to take theoretical physics even though it’s not required.

I’m not quite sure what this all means yet, and there’s other issues at play that I haven’t described, but I’m thinking hard about this. The issue of navigating multiple communities is complex, and I’m hoping by choosing to write about some of this that I will develop some insight into what this all means.

 

 

One interesting physics conversation this semester has been about how we categorize forces. One future physics teacher in particular kept being concerned about whether to call something a tension force or a normal force. For example, consider the following situations:

• A chain, consisting of many links, hangs vertically. The very top link has a rope wrapped around it, which keeps the whole chain fixed to the ceiling.
• A rope is wrapped around a box and pulled by a person.

What kind of contact forces act on the top link? What kind of contact forces act on the box?

I think many students learn to associate types of forces with kinds of objects. For example, objects like ropes and strings exert tension forces. Objects like walls, ramps, and tables exert Normal forces. Springs, of course, exert spring forces. This kind of object-focused categorization means having to have a category for forces from a hand, like “Applied Force”

If this is how you think about forces (in terms of object categories), both the link and the box have tension forces exerted on them by the ropes, because ropes exert tension forces.

Another way to talk about forces, however, is to focus on mechanism. This is how I, and many other physics teacher I know, talk about force. Normal forces are contact forces arising from surfaces or points of contact that press into each other. In other words, Normal forces are compression forces. Tension forces are contact forces that result in points of contact that involve stretching. Friction forces involve sheer. Compression, tension, and sheer are about what’s happening at a point of contact not about what kind of object is exerting the force. A hand that pushes, of course, is just a normal force, because your skin cells are being squished not stretched.

It took me a while to really get insight into the students’ concern, but as we talked more and more I realized his concern resulted from the juxtaposition of these two ways of categorizing force. In the two scenarios above, the part of the rope that is contact with the object is being compressed. If  one is attending to the mechanism, then you’ll conclude that it’s a Normal force. If you are focusing on the kind of object it is, you’ll conclude it’s a tension force. This contradiction troubled the student.

The question remained, however, how should we resolve the conflict? At first, I was being a very bad debater. I just kept repeating my own arguments about normal forces being compression, dismissing altogether the issue of what kind of object it was. Now, I do think that categorizing based on mechanism is more useful than categorizing based on objects, but merely repeating my view was not going to help us understand the real issue. It wasn’t helping either me or the students get a deeper understanding. The real issue came about by thinking about grabbing someone by their shirt and pulling them toward you. In this case, if we choose the person’s naked body as the object of analysis, then the shirt is compressing against the person’s back pushing them forward, meaning there is a normal force. However, if we choose the object of analysis to include their shirt, then we could conclude that the shirt/person system was experiencing a tension force. If you get really picky about the exact boundaries and how the hand grabs the shirt, you might even conclude that the force exerted by hand on the shirt/person  are some combination of normal forces and friction forces. The key point is that we could certainly draw the boundary somewhere around the person (e.g., including most of but not all of the shirt) where the force at the boundary is a tension force.

The thing we realized is this: The ambiguity about whether something is compression or tension goes away when you attend to both mechanism carefully and attend to system boundary carefully. Small changes in the exact location of the system boundary (naked body or naked body + clothes) matter for whether the points of contact at the boundary are in tension or compression. That’s because even a single object can have places that are in tension and that are in compression. If you slice the boundary over a region that is compressed, your going to have normal forces. If you slice the boundary over a region that is being stretched, your going to have tension forces.  The shirt example helps, I think, because of it’s a subtle shift in boundary.

With the rope around the box, if you are serious about only including the box in your system, then there is no tension force. However, if you drew the boundary around the box a bit farther out, such that the rope around the box was in the system, then the force acting on the system is a tension force. The truth is, as an object, a lot of the rope is in tension.  One thing you realize in thinking about this is that tension forces can’t arise with out adhesion or bonding.  If you haven’t adhered a rope to an object, it can’t exert a tension force.

What’s interesting is that this is the complete opposite of what I’ve often heard said to students. Students are often told that ropes can only pull, not push.

 

 

This year in inquiry, we started with light as usual, but now we are moving on to energy. We’ll be conducting our own energy inquiries as we also analyze and discuss Sharon’s 3rd-grader’s inquiry into energy at the Responsive Teaching in Science Website, reading the book she co-authored called, “Becoming Scientists“, and talking over skype with Sharon about teaching science.

Below are excerpts from students’ first assignment that are still coming in. We have actually not discussed energy at all in class. Students were asked to write about an object or activity in their house that they think involves energy. Here is just a peek into what students are writing:

I think that fans are powered by electricity/energy and this allows them to move in a circular motion to create air flow.  This makes sense because in order for something to move it would need energy.  To me, it has always made sense that anything moving has some sort of energy asserted on it.  Usually when things move other objects, then the object gives energy and the object receiving the energy is using it.  I think that energy is needed in order to make fans work because without energy it just wouldn’t move at all.  The fan wouldn’t have anything to power the engine.

I know that light uses electricity which I think is powered by energy.  I know the term “electrical energy”, so this leads me to believe that electricity is either a type of energy itself, or is powered by energy.  Energy has to be present for the light to turn on.  I believe that energy sends electrons to the light and the electrons make electric energy which causes the light to turn on.

I do know that there are different types and different ways energy is transferred and/or released. I know that the energy starts somewhere and is transferred through wires through an outlet in my home. Then, the energy is transferred again through a lamp, air freshener, or TV. My question now is where does energy begin during this process? I understand that energy can move from source to source but where does it begin in this scenario? For example, a child pushes a ball. When the child pushed the ball, energy was given off and transferred onto the ball. What is the “child” if you will through using an electric outlet?

Energy results in an action. A lamp being turned on is evidence of a change or an action. Energy had to be used to create that change. Energy was transferred from the outlet to the source in this case, a lamp.  Energy is needed to make this action happen because a lamp is not going to turn on itself. A TV needs another source to “wake up.” The way I look at it is this way: everything is at rest, there must be an action that “wakes up” an object to get reaction desired. In this example, energy is being used through electrical outlets. Energy transferred through wires to the electrical outlets, this process causes many different objects to “wake up.”

When I think of energy, I think of any type of movement: Even if an object only moves or works because of another source of energy—the stationary object is still using energy.
In the case of playing the piano, I am using energy in all sorts of different ways.  In a sense, I am “giving” or “transferring” my energy to the piano to make sound.  I think of energy almost like a chain reaction or domino effect—the energy used or transferred happens so quickly that it’s almost unbelievable!

In physics licensure, students were working through a tutorial about tension. The tutorial guides students through a series of scenarios and questions to generate the reasoning behind the approximation that tension forces exerted on/by both ends of a very light string are equal in magnitude.

Near the end of the tutorial, students apply this knowledge to the Atwood’s machine. The first case is where there are equal masses on both sides , but the masses are at different heights. Based on intuition, some students expect the masses to stay put , but others expect the higher mass to descend in order to match heights .

I nudge students to subject their initial ideas to further analysis. Students conclude correctly that each mass has two forces… Tension up and weight down. The students also reason that the weights are same because the masses are the same. They also reason that the tensions must be the same by the small mass approximation–not by Newton’s third law!

For the student who anticipated that the masses would balance, this looked like proof. Everything is equal and balanced.

For the student who wasn’t sure if they would balance, this was not settled. The student noted that while we knew the tensions were equal and that the masses were equal we knew nothing about how the tensions compared to the masses. So true.

Eventually, with probably too much help from me, we sorted this out using proof by contradiction. Let’s assume that the tension is greater than the weight. If that’s the case , then both masses would accelerate up! Which is impossible, both intuitively, and logically based on the constraint imposed by the rope. You get a similar contradiction if you assume the tension is less, with both masses descending. You are only left with the possibility that the tension is equal to the weight. Both masses sit still perfectly content to be at different heights.

What I loved about this moment was the following:

(1) Being a scientist in this moment was not about knowing the right answer, but rather about pursuing reasoning to help settle a matter.

(2) The person holding us accountable to rigorous reasoning was, in fact, the one with the wrong intuitive prediction. The person who was confident of the right answer was actually briefly convinced further of their answer by incomplete reasoning.

(3) While everyone at the end was convinced of the correctness of final reasoning, the student with the initial wrong prediction wanted to see it to believe it.

That’s a lot of science in there–argumentation, application of newly learned scientific tools to settle disputes, offering and critique of lines of reasoning, and insistence of empirical support for theoretically drawn.

In intro physics, after exam one, I like to let student give me feedback about how class is going. That feedback is about what happens in class. After exam two this year, I want them to think more about themselves and how they are spending time outside of class. So, here are today’s clicker questions: Am I being to confrontational?

 

I read the lecture material

A. before class, annotating the text to enhance learning, taking notes for myself about what I do and don’t understand.

B. ahead of time, but not close enough to really learn or be prepared for class.

C. Eventually, but never before hand. I don’t really stay on top of it.

D. Not really ever. I maybe just skim it eventually for formulas and to look at solutions.

 

I work problems…

A. Regularly from the end of the chapter, taking note of what I am doing well on and what needs improvement.

B. Sometimes, but not regularly enough or in a way that’s useful for me learning.

C. Seldom, but only really in the days leading up to the exam.

D. Not much at all. I just look at solutions.

 

I apply for reassessments

A. Regularly to get extra opportunities to practice and to get feedback on how I’m doing.

B.  Sometimes, but I wait too until it’s too late and don’t do it often enough.

C. Never, but I want too. I’m too disorganized in my life to remember.

D. Never and I don’t even think about it.

 

I read about the lab activities

A.  Before class, so my group can be efficient in how we spend out time. This gives our group enough time to nearly finish the lab in class, so there isn’t too much left to do outside class.

B. but only in a glancing way, so we end up wasting time in class not understanding what the lab is about. We never finish lab in class, and we are left with lots to do.

C. Never before class. I’m almost always confused about the labs.

D. Wait, we can look at the lab activities before class? Wait, the syllabus shows a schedule of what labs were doing each day?

 

 

A. I read the appendix of the lab activity book to learn about uncertainties, graphing, and how to linearize graphs.

B. I have looked at the appendix, but I don’t put in the effort to learn from it. I sort of blame the text for being confusing.

C. I know that there is an appendix, but I haven’t really looked at it closely.

D I didn’t even know that there was appendix.

 

I have met with Brian

A.  On multiple occasions when I didn’t understand something

B. The week of the exam.

C. Never, but I always say to myself that I should

D. Never, and don’t even think about it.

 

I have…

A. Been to free tutoring on multiple occasions.

B. Gone to free tutoring once.

C. Never been to free tutoring.

D. Not been aware of free tutoring.

 

When Brian gives us choice in class,

A. I’m always using that opportunity to practice extra challenge problems and questions he gives us.

B. I sometimes scramble to finish an old lab and sometimes get a chance to practice.

C. I’m always scrambling to finish old work, and never get extra chances to practice learning in class.

 

 

I’ve been asking students to use more sentence frames to structure writing in inquiry. I’m trying to strike a balance between giving them freedom to write in ways that allow them to express themselves while also giving them structure to work within.

For example, a few weeks ago, students had to make two diagrams–one depicting how light from a stoplight would enter a pinhole camera with a small hole and large hole. I asked students to use the following sentence frame to describe each feature of their diagrams.

In the _________ part of my diagram, I am showing how __________. This is important to show, because __________________.

Then to compare and contrast their diagrams, I asked them to write.

In my first diagram with the small hole, you can see how __________. The reason I think this happens is because,_______________________________.

In my second diagram with the large hole, you can see how __________. The reason I think this happens is because _______________________.

One reason I have found this useful is because it helps students to think about their diagrams in an dialogic way. You try to craft your diagrams to actually show things you care about, but you also let the diagrams speak to you to tell you things you might not have known. Another reason I have found this useful is that it makes it easier for students to read each other’s work, because it’s in an easily comparable format. Third, it significantly reduces the number of assignment that are way off the mark.

In a recent assignment further exploring blurriness, I gave student freedom to begin their writing assignment, but the assignment had to end with and lead up to the following sentence frame:

To me, a clear image is made when ______________________________, and blurriness happens when ___________________________________. Based on my ideas, in order for a lens to change a blurry image into a clear image, a lens would somehow have to ________________________________. I’m notsure if this is right, but it might make sense because ___________________.

In this sentence frame, I’m trying to get them to think about implications of theory. We have five different theories of why a large hole causes blurriness, some that seem quite different and some quite similar. The theories are

(1) A big hole is like a lot of small holes. Since a small hole places a clear image, multiple small holes would make multiple clear images that are juxtaposed. Those images being in slightly differently locations makes it like you are seeing in “double vision”.

(2) A big hole allows light to expand and spread out more. When light expands and spreads out, it loses it’s clarity and the intensity of light weakens.

(3) A big hole allows in too much stray white light. This stray light “whitewashes” the image making it fade, which is why it looks blurry.

(4) A big hole causes light from one point on an object to land in a “blobspot” rather than a precise location. Large “blobspots” make for a bad image in the same way an old TV with large pixels.

(5) Same general idea as #4, except blurriness is caused by overlapping “blobspots”. It’s the overlapping of of blobspots that makes it look like a blob rather than an image.

On the assignment, students were supposed to elaborate on and diagram their favorite theory (or combination), but I wanted them to start thinking about implications. If blurry is “too much light”, what might a lens have to do to make in unblurry. If blurry is “too big of blogspots”, what would a lens have to do to make it unblurry” Etc. In getting them to think about implications of their theories for lenses, I’m hoping to prepare them for transfer as move to talking more about the eye.