Physics Pub Questions

One of the students in our physics teaching program has been organizing, “Physics at the Pub” events. Basically, a bunch of us get together to talk physics over beer and food. So far, we’ve met twice, and we’ve had some really fun, interesting conversations.

The first time, we talked about this question. “Why when you pour beer in the pint glass does it seem like the beer extends all the way to the very edge?” Like we know (and can see when the beer isn’t there) that the glass boundary has a definite thickness to it. So the beer must really be “inside” of the glass rim, but it looks like it extends all the way into the glass.

Last night, we started off by talking about the Veritasium’s bullet in the block question, but spent almost all the time talking about this situation: Why does a soccer ball go farther than a bowling ball when you kick it? Most people’s initial response is that “same kick” = “same force”, and thus by Newton’s 2nd law “Same force over more mass means less acceleration”, and then finally “less acceleration means less distance”

But, pretty quickly the discussion comes to be about what “same kick” means. It turns out, there are lots of reasons to be suspicious of the assumption that the “same kick” results in the same force, but it’s challenging work to reconcile that with the commonsense idea that you “kick with a force”.

What I love about this second question (which I’m pretty sure I was introduced to by David Hammer), is that, for students, resolving it involves having to really contend with many, many concepts all at once: what force is and isn’t, the limitations/challenges of Newton’s 2nd Law reasoning in the context of non-constant forces; their level of commitment to Newton’s 3rd Law, carving out how we should think about the magnitude of acceleration in concert with the duration of acceleration, impulse and momentum ideas, inertia and what we mean by that, and struggling with how t think about the “stiffness” of materials (and modeling that with springs). Energy typically gets in the mix as well. 

The second thing I love about the question is this: Everyone knows the answer. The soccer ball goes farther. We just can’t agree on how to adequately explain it.

The third thing I love about the question is this: It reminds me that, if you want to find out what students think and/or engage them in deep physics, you don’t need an elaborate/ contrived scenario. In fact, the more everyday and seemingly simple the situation is, the more likely you are to engage their thinking. That said, this question should be probably saved for students who have a good deal of facility reasoning about Newton’s laws and who are likely to recognize the need to persist in trying to reconcile inconsistencies.


Rambling– or Interesting Things I would blog more about if I had time

I.  A clear majority of students in my physical science course for future elementary school teachers do not actually plan to go into teaching. When I ask why, they say that it’s because teachers they have come to know and/or meet all tell them they should “run away” as fast as they can from public school teaching. 

II. Because I am teaching 2nd semester physics, I have many more students with whom I interact for an entire year. I enjoy having these year-long relationships with students, because I get to know students much better. There are also real big advantages with the amount of trust that students have with me. We can do things and persist in things that are confusing, because they have been there enough times with me to know that it will pay off, AND that even if one time it doesn’t pay off, it’s OK, next time it will.

III. In my step II class (the 2nd course in the UTeach sequence), a hot topic of discussion from students has been their own challenges and successes in “getting students to say what you want.” This phrase comes up so often in class (from students, not the instructors). It’s a real window into how they are conceptualizing inquiry teaching so far. While I understand that they are grappling with the very real difficulties of asking good questions and facilitating discussion, their language here suggests that the students and I have different views about the purpose of questioning and discussion. I don’t think they yet see that questioning and discussion serves a role in helping the teacher (and students) find out what everyone is thinking. 

IV. Several of the physics teachers in our area have really taken up some of the discourse moves we have talked about and practiced in our monthly workshops. One teacher in particular says that “re-voicing” and asking students to “re-voice” has transformed her classroom practice. While many teachers really enjoy our workshops, some really “take up” practices more readily than others, and I’m curious about when and why this does and doesn’t happen.

V. I have an amazing group of students in my physical science class. We do lots of serious intellectual science almost everyday, and do it while having a lot of fun. It is so much fun to be in that class, laughing all the time. Yesterday, I had to kick students out of class (30 minutes after it was officially over), so I could start my other class in the same room. I wish I could tell you more.

VI. Being in my third year working with the future physics teachers has its advantages. Before, almost every student I knew was “new” to me, and getting students to “come around” was hard work. Now, I’m almost never teaching a class, where there isn’t a mix of students that are new to me, some I know a bit, and some I know really well. This has huge advantages, because the newer one’s learn how to “participate” implicitly by observing how the more experienced one’s participate. Students more quickly and readily pick upon the fact that “you have to talk”, “share and listen to ideas”, “defend your ideas with reasoning /evidence”, and importantly realize that we all understand the physics less than we thought (and that it’s OK to be wrong and admit you don’t understand something). 

VII. I am almost always barely getting by in doing what I have to do. It is stressful, but for the moment, things are going really well, so it makes it feel so worth it. While I’m quite content right now, I have to admit to myself that I don’t know how to get an appropriate work-life balance. I know that my current balance can’t go on forever, and I’m struggling to see how to make it work. Ugh.

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