Teaching Methods

Pumpkin Projectiles

You can smash your Halloween pumpkins! Each year at our science center, Discovery Center Museum, they will launch your pumpkins (up to 8kg) with their 10 ft trebuchet which is loaded with 400 lbs. (Why they limit by kg, but load with lb, I have no idea)

As a last minute thought, I blasted a text to my students: determine the initial launch velocity of the pumpkins. Double the points if you confirm the presence or absence of air resistance. Present in claim, evidence reasoning form. Have it ready for Monday.

Naturally, I couldn’t let my kids have all the fun (or the answers) so we went together as well. The pumpkins go way too fast/far/high to collect enough data at 60 fps, so I filmed in slo-mo (here is the original video), tracked the pumpkins on Vernier’s Video Physics app…

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Of course, I had to see the graphs right away…oh so pretty…

then loaded the spreadsheet into excel and adjusted the times for the slow-mo camera. Additionally, since I had been given the specs in feet, I had to convert the units to meters. (I used the length of the base of the trebuchet to set the scale).

 

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Can we just discuss the beauty of these regressions? The vertical velocity is broken into three parts: the launching, from release to peak, and from peak to ground. You can see how quickly air resistance comes into play. The weird fall off tail is where the iphone goes back to 60 fps in the last moments of the video

 

Oh how beautiful thou art, quadratic functions! Yes, air resistance is a factor, slowing the acceleration to about 3 m/s/s. There’s also a horizontal acceleration of about 1 m/s/s as well. Launch speed worked out in the ballpark of 12 m/s.

My kids who went are still crunching their numbers…we’ll see what they can produce!

 

Teaching Methods

Modeling vs Intentional Modeling

“I use modeling, do you?”
“Uh…no, but I’m interested in learning about it”

I felt like such a noob when I had this conversation a few months ago because literally, everyone else at my group seemed to be doing this already. I was at a workshop on whiteboarding after a talk on standards-based grading and modeling and I thought, “wow, she really has it together… I have a LOT of work to do” (Does anyone else have this overwhelming feeling of inadequacy in the classroom all. the. time. or is it just the mom-guilt extended into the classroom?)

So I have started incorporating some things here and there as I’ve gone along, and I recently looked into Etkina’s resources (I started using parts of her book last year). As I poured over Etkina’s labs and our workshop speaker’s resources I realized: I HAVE BEEN DOING MODELING ALL ALONG! Mostly because it’s just the way I already think about problems. It just didn’t have a fancy name, and more importantly, I wasn’t always doing it intentionally as a teaching strategy.

I’ve decided that the intention is really the key in modeling as a teaching strategy. I think good physicists are good at models but bad at teaching them. We do it so seamlessly in our own work we fail to realize that type of thinking is not seamless or natural to the general public.

Cue modeling curriculum

Models are just any representation we use for a situation: pictures, free body diagrams, motion diagrams, graphs, mathematics etc. We need to work our kids like gymnasts, very intentionally using and practicing these models so that our students become flexible and natural at using them on their own for any scenario.

This is the paradigm shift: teach the model first, and the physics as a result of the model. Too often physics teachers (especially physics teachers not trained in physics) teach all this physics stuff, then all these equations for particular problems and then maybe shove in some graphs at the end. The problem is that students fail to see the bigger picture and physics becomes a class where students are attempting to memorize a million procedure for a million different problems, rather than learning a handful of approaches and selecting the best one or two for the problem at hand. The clearest example of this in my current classroom is how I am teaching two-body problems. I have made a huge deal about the fact that all of the physics is in the FBD. Because learning the general process for FBDs is a lot easier than trying to memorize separate processes for ramps, Atwood machines, modified atwood’s and oops! Now there’s friction!

The next most important part of this is to teach students how to communicate with one another using their models, and this is where the value of whiteboarding comes into play. I believe very strongly in letting the kids move around the room to see whiteboards without having a board representative at each board. The reason for this is that the students begin to realize that it’s hard to make sense of what someone has done if you don’t provide enough detail. Students can then ask these questions and leave them at the board before we come together as a whole group for discussion.

I decided to use modeling very intentionally in the classic coffee-filter air resistance lab. The original lab I had snagged from someone had a bunch of background info and then asked students to skets the velocity and acceleration graphs. I got really tired of marking the same things on everyone’s papers last year and realized this year that this is a perfect opportunity for modeling.

When students walked in today their desks were in groups of four with a whiteboard. I asked them for the following

  1. A free body diagram at t=0, sometime before terminal velocity, and at terminal velocity
  2. Acceleration expressions for each of the diagrams
  3. position, velocity and acceleration vs time graphs.

IMG_1632It was so cool to watch them work, discuss and argue. The FBD’s were relatively easy, the discussions mostly about whether or not to put air resistance on the t=0 diagram.

The discussions about the graphs were far more interesting. Many students were working with the graphs as unique units, rather than considering the relationships from one to the next. Inevitably we had piecewise acceleration graphs and linear acceleration graphs and linear piece-wise vs curved velocity graphs.

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I asked the kids to cite similarities and ask questions about differences. One group today started changing their board before attention was drawn to them. It offered a fantastic opportunity to review the graph models and review the relationships.

One of my favorites was a group that decided the curve of the velocity graph was quadratic, so they started taking the antiderivative for the position function. They noticed the constant slope portion in many of the other graphs and asked the question about it. Then they realized (#overachievers) the velocity graph wasn’t really quadratic.

I realize this particular example isn’t quite model-based learning through and through as I did not allow them to experimentally discover the exponential function relationships, rather after discussing that all of these changes were continuous I gave them a brief taste of the calculus/diff eqs ending in “solution is always in the form….” and hey, doesn’t that look like the curve we agreed upon?

We only collected data today, so I’m really curious and excited for what their write-ups are going to look like Wednesday!

I’ll keep you posted 🙂

 

 

Teaching Methods · Uncategorized

Teaching to Reach the Introvert

My second-grade teacher called my mom concerned that I didn’t play with any of the kids at recess: I read a book under a tree instead. When my mom asked if this was a problem the teacher reported that I wouldn’t have any friends. I was elected to represent our class for the school council that year.

Research indicates that as much as 50-74% of the population is extroverted. It is generally viewed as a valued quality: put yourself out there, be friendly, be social. These are the rules society dictates whether it is on the elementary playground or in the workplace. Our culture favors extroversion, and many of the qualities associated with introversion are erroneously viewed as a failure to be able to advocate and insecurities with oneself.

Nowhere does extroversion seem to get a higher reward than in the classroom.  There is a huge emphasis on team and group projects, and the excellent teacher is often seen as the one where energy runs high in the room, rather than examining student behaviors and conversations. During the majority of my high school experience, most classes had a participation grade. If I did not speak in class I was guaranteed nothing higher than an 80% for participation, regardless of the fact that the rest of my work was A-work. I despised the participation grade. Some teachers pride themselves on their use of the Socratic method, but research has indicated that it’s execution this can offer the opportunity for gender bias: male students are more likely than female students to shout out or offer answers to questions, regardless of if they are correct. Teachers, in turn, are more likely to respond to those students and the quiet students are left in the dust.

I want to make perfectly clear that I am in no way, shape or form suggesting that classroom participation, presentations, and conversations should be abandoned, far from it! All of these skills are important and required for any field and for success. At the same time, if we are trying to reach all students in a way that they learn best, then we have to offer comfortable environments for the introverts in addition to the extroverts.

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One of my extroverts discussing the solution to the problem. All students in this group worked on the same problem in pairs, then came to consensus before presenting to the class

Science is all about collaboration and presentation. Students who think otherwise are in for a very rude awakening as they approach their senior year of college and enter the workforce or graduate school. A method I have recently adopted is whiteboarding. At the spring meeting of the Chicago Section of AAPT, Kelley O’Shea presented on standards-based grading in physics and lead a workshop on whiteboarding methods. (See her blog!) One of the most important aspects of whiteboarding (and teaching, for that matter) is fostering an environment where it is safe to share and safe to be wrong. In the lab setting, this consists of all of the students putting their lab results on a large whiteboard and standing in a large circle. Students comment on similarities and ask questions about differences on the boards.

 

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Sample board and commentary from students. Students assess each other’s final answers and reasoning in addition to the quality of the presented work. 

I have used this method in my teaching, but I have also included a variation on the model. Occasionally (and in the interest of time and space) I have students circulate the room to examine each of the boards. They are still asked to consider similarities and differences, but I ask them to write questions and comment down on a smaller whiteboard next to each of the large ones. After we have done this, students return to their boards, read the feedback and then I open the floor to comment on similarities and differences. This provides the introverts with a huge advantage: they still get to collaborate in their small groups, but they receive the wealth of information in the large group as well as having another avenue to participate in the whole group discussion.

 

The second whiteboarding method I find to be highly effective with my introverts, shy students and students who struggle is what Kelley fondly dubs, “whiteboard speed dating”. In this exercise, students are paired at a board and the entire class is given the same problem. Here’s the catch: the problem is goalless, it does not end in “calculate the _____”. Students are two write anything on the board they can (diagrams, equations, graphs, etc) in the time allotted (1-3 minutes). When time is up, partners split, everyone moves around the room to an adjacent desk and now they have a new board, a new partner, and a new perspective. The first time I tried this I, admittedly, was anxious for my most introverted student. She did not speak. ever. even to me. ever. even when asked a question. about anything. Within 3 rotations she was explaining the problem to her partner, and I’ll add: not a student she typically worked with. Working in this manner gave her the confidence to collaborate with another student. Would she get up in front of the class and explain the problem? Not today. But maybe eventually.