The main goal today was to understand how to calculate the force of gravity and force of friction and to understand what factors affect the strength of each of these. Students started class by doing stations labs (90 seconds each, no writing, just doing), then discussing what they learned with a partner from another team. We then applied this to solve simple situations involving Newton’s 2nd Law.
We took a test today in AP Physics C, our first test this year with all old AP Questions. At this point in the year, I give students about twice as much time on tests as they will have on the actual AP Exam. The thought behind this is that at this point in the year we are developing mastery of skills, concepts, and processes, and not concerned about speed. Later, as we get closer to the semester final (a full length Mechanics Practice Exam) and the actual AP Exams, we practice speed. Its kind of like building up mileage over the summer as a distance runner, and then working on speed work as we get into the competition season.
I have been using the multiple choice question bank in the AP Classroom this year. The user interface is clunky but has the benefit of providing access actual AP Exam questions to students on their phones. While not many of the questions on the question bank are new (I had access to most of these after attending an AP training), I have decided to use only the questions on the AP Classroom when creating tests. After students take the test, I quickly score their MC test by checking it against a key just to get a total score. The next class students enter in their answers for each question on the AP Classroom to find out correct and incorrect responses. Even though the user interface isn’t great, I’ve decided that the effort creating tests using these questions banks is worth it so that students will have access to these questions to review from throughout the year.
We did our post lab discussion today for the Unbalanced Force Lab. This was our first time following the process for an Argumentation Session (we did this on Day 18 of AP C, I described the process there). This process has a lot of similarities with modeling style post-lab discussions. One difference is that students are basically creating an outline of the argument that they will use for their lab report. After graphing their data and creating an argument on a whiteboard, students did a gallery walk session for students to get and give feedback on their whiteboards. The main topic of discussion was the meaning of the slope and intercept (some had positive y-intercepts, others positive x-intercepts). Many groups felt very confident in their rationale for what would cause the intercept. The discussion about slope was more challenging (the slopes ranged from 0.5 m/s/s/N to about 2, caused by system masses ranging from 2000g to 500g).
After the argumentation session, we discussed the requirements for the lab report (we are following the ADI format, with a few changes). Students took pictures of their boards, which they will use as an outline for their lab report.
Students did a Peer Review through http://www.turnitin.com today for our first formal lab-write up of the year. (Turnitin is a paid service, I’ve heard good things about PeerReview, a free service too).
Today was also our review day for the forces unit. The main strategy was “Expert Groups.” Students had completed one of 4 FRQs that involve forces as homework. In class, they worked with other students who completed the same FRQ to become “experts” in that particular one and then went back to their original teams to share the general processes and concepts involved in each section and then explain what they thought was the most challenging part and why.
We also practiced linearization today. Specifically, how to choose an equation that describes the relationship between the variables in the situation, how to plot data that will create a linear graph, and then figure out what can be calculated from the slope of this graph. This year we did this as a whole class (each team solved on a whiteboard). Next year I hope to turn this into a Guided Inquiry Partner Task.
We are following the Argument Driven Inquiry format for this lab. The Guiding Question is: What factors affect the acceleration of a system? After a pre-lab demonstration (one student using a spring scale and rope to pull on another student riding a skateboard with a constant force), the class created a list of factors that could influence the acceleration of a system. We then chose to investigate this question by studying the relationship between force and acceleration, with the goal of finding how the other factors that students came up with (friction, mass, air resistance, angle of the track) affect the acceleration was well by analyzing the slope and intercept of the graph.
This lab also presented an interesting materials challenge. We didn’t have enough pulley brackets or end stops for the full class. I was able to 3D print enough of each. My wife also helped me design a “sled” that I 3D printed to hold the weights on the cart, instead of taping or bolting the container for our weight sets onto the cart. I was only able to 3D print a few of these this year (each print is 8 hours), but plan to print enough to use them on all of our cars next year. If you have access to a 3D printer, here’s a link to the .stl file. I printed mine in PLA on a Monoprice Mini ($200 on Amazon!). The print bed of my printer is 4.5″, which limited the size I was able to make it. It fits both the old and new Vernier Dynamics carts.
After attending an Argument Driven Inquiry (ADI) workshop, I decided to use this for our current lab in AP Physics. Specifically, I would love to make the formal lab write-ups that students create more authentic. I have been following a Claim, Evidence, Reasoning, Application (CER-A) format. This format has its benefits, but I saw improvement in the format presented at the ADI workshop: Introduction, Methods, Argument. The argument section is formatted very similarly to CER-A, which is what my students are used to, so it seems like a good switch. One of my hopes for changing to this format is to give students a bit more freedom in how they approach and answer the Guiding Question to make their responses less formulaic.
In today’s lesson, students analyzed their data as a team (my rule for today’s lab: they must use linearization to answer the question). Then, as a team, they created a whiteboard to display their argument. I didn’t make enough time in the lesson for them to give and get feedback to improve their whiteboards, but I wish I had. Students are using these whiteboards as an outline for creating their lab report for this lab.
One of my favorite days of the year: Broom Ball Relay! This is our introduction to the Forces Unit, used by lots of modelers. The activity is really fun and is one of the most central lessons that we draw back on throughout the course of the year (and in AP Physics too). We set up a relay course on a flat, smooth indoor surface (the gym works great when it is available). The Essential Question we used was “How are forces, motion, and inertia” related? Students participated in a relay course by pushing a bowling ball from one end to another. This included making a hard turn, making the bowling ball travel through the ‘no touch zone,’ and getting the ball to come to a complete stop at the start/stop box. Quite a few students either made the same mistakes as those who went before them (“it’s harder than it looks”), but some also learned how to perform parts of the course well and coached their teammates through the course.
The best parts of this are how evident it is that it is hard to turn the ball once it is moving fast, the fact that the ball moves with a constant velocity in the ‘no touch zone’ and also how difficult it is to stop the ball in the start/stop box (the ball isn’t stopped until a Physics teacher says that it is stopped). For years, I have watched students push the ball in a way that makes it move in circles, over and over, just inside the edges of the start/stop box. Instead of getting the broom out in front of the ball and pushing against it’s motion to stop it, it is common to keep pushing on the side of the ball, making it turn. Often, the student looks up with a worried look when it becomes evident that this isn’t working. I have come to realize that (I think) that these students are attempting to stop the ball by pushing it into the center, not knowing that this is exactly how circular motion is made. This becomes an important discussion point and becomes a key idea in our Central Force Unit later in the year.
After the activity, we debrief by connecting this activity to the ideas of force, net force (or ‘sum of the forces’), and inertia.
I attended a full-day Argument Driven Inquiry workshop today. I had heard about it from Middle School teachers in our school-district who love using this process with their students. It sounded transformational and I was interested to hear more. We did a “blood typing” lab in teams and created the following whiteboard to display our argument and get feedback from other teams on how to improve our argument. Thanks to the other teachers in my group, I learned a lot about biology that I didn’t understand before. I also loved learning about the process of having students work together in teams to develop an argument, get feedback, and then create a lab report that uses the argument that they created as a team as an outline. I see a lot of qualities that are similar to the modeling pedagogy, as well as some big differences that I hope to implement soon.
Students were introduced to, and collected data for the Drag Force Lab today. I am trying out the Argument Driven Inquiry format for this lab, which has a lot of similarities to Modeling.
Before class, students had completed a pre-lab assignment where they read background information about the lab and answered questions that involved drawing motion diagrams, force diagrams, and graphs.
In lab, students first discussed 3 different pre-lab questions with their team (similar to, but different from the homework assignment) and answered the questions on a whiteboard before collecting data. Our Guiding Question for the lab is: Is the relationship between velocity and force for something moving through the air linear, quadratic, cubic, or something else?