At the AAPT Winter Conference, I attended a workshop on the Reformed Teaching Observation Protocol (RTOP) (emphasis on “reformed teaching” not “reformed protocol”). Below are my notes on that workshop. [This workshop runs 8:00-5:00 on Sunday, and I’m live blogging this so, if you’re reading during this time, reload the page for the most up-t0-date content.]
Intro question: What does good physics learning look like?
Student engagement: hands on; notetaking; calculators/computers use; students doing things, not just passive
Teacher engagement: focus on different groups of students; listening to students; circulating around the classroom; during lectures responding to students questions, circulating.
Today as a finals review “warm up” (although it ended up taking the whole period) I presented the students with four beakers of water: One with ice, one at room temp, one on a hot plate “low” (about 37C) and one boiling. I used Logger Pro to show the four temperatures on a projector screen (a sensor in each beaker). I asked them to use the skills they have learned in this class to analyze the relationship between temperature in F and in C. Half the class I told to set C as the IV, half F as IV.
On the Physics Modeling email list there has been a discussion of finding tangents to a parabolic curve using an Excel spreadsheet. The primary way we use this is when students graph position vs time of a ball rolling down a ramp. Students discover that the relationship can be modeled as a parabolic equation, x = at2+bt+c. If they can calculate the slope (velocity) at various times, they can then graph velocity vs time, and discover that this relationship is linear.
I have created a spreadsheet that will allow students to enter the their (1) quadratic function values, (2) Independent Variable range, (3) a chosen Independent Variable value and (4) the increment above and below it. The spreadsheet will then calculate and graph the “tangent” at that point (not exactly the tangent, but if they chose a small enough increment, it will look like a tangent).
In my physic classes, we do a lot of labs. Students are encouraged to create their own data tables, but many aren’t so “linearly” inclined, and have difficulty creating neat tables. I created a generic data table they can use on any lab.
Design of the data table
Most of our labs require three measurements of ten different settings of their “independent variables.” I suggest to my students that if their first three measurements don’t look “close enough” to each other, then they repeat it again and see if:
any one of the now four look like “outliers” probably due to a mistake in their work on that run, or
if their results just have a large spread probably due to the low precision of the experimental design.
The data table includes a couple extra columns with this in mind.
We generate a rough outline of the lab procedures, but students often have to make decisions about the specifics of their lab. Thus there is a section for “Notes before conducting lab” and “Notes after conducting lab.”
At the AAPT meeting in Ann Arbor, I presented a poster on concept mapping in physics classes. An idea that arose there was the creation of a concept map of the ASU Modeling Cycle, so I created one. Take a look and let me know what you think. I’ll probably make adjustments to it when I get suggestions.
Many physics teachers do a “target shoot” lab for conservation of energy. The basics of the lab is that students roll a ball down a curved ramp and predict where it will land. By calculating the change in gravitational energy from the top to the bottom of the ramp (“Phase A” in the sketch), students can use this as the kinetic energy at the top of the drop (“Phase B” in the sketch) and calculate the velocity of the ball (at this point all horizontal). They then calculate the distance the ball will land from the table.
The key is they don’t get the ball until they are ready to take the test (otherwise some will roll it down the ramp and record where it lands). You can either give them the mass of the ball, or point out to them that both gravitational and kinetic energy use mass, so it can be canceled out when you set Eg = Ek
Note: I use the Modeling Instruction symbolism “Ek” etc. instead of KE, to emphasize to students that all energy is the same, just stored in different means–this symbolism follows standard physics/science symbolism of using a large letter for this concept (e.g. Energy, Friction), and adding a subscript for the different types (e.g. kinetic and static for friction, kinetic, gravitational, elastic for energy).
I first did this with a cup with clay in the bottom. Students would place the cup where they predicted the ball would land, then roll the ball down and see if they were accurate. But I’ve since come up with a target with grade letters on it. Once the make their calculations of where the ball will land, they carefully line up the ramp with their target (I put + and – sideways on the target, since this “lining up” is more eyeball than physics). Once they have their target taped on the floor, I come around with a piece of carbon paper (many students have not seen this before) and place it on top of the target. I then roll the ball off the ramp three times, and they get the average of the three results (usually all three dots are very close to each other). It’s always great to see their faces as the carbon paper is lifted and they get to see their grades!
One caution on this lab: about 25% of the gravitational energy is converted to rotational energy, so the results are not where they predict. In my class, I simply point out to students that to get a ball rotating, work is required and thus some of the gravitational energy is converted into this rotational energy. In their calculations, they deduct this 25%, and their results are excellent. With more advanced classes, students could calculate the rotational energy themselves.
Below are the handouts I use with my students. The tutorial walks them through the process, so you may or may not want to provide it to your students.
Yesterday I took a trip up the longest elevator ride in San Francisco (at 555 California St). I brought along my LabQuest and Force Plate (essentially a recording bathroom scale, see image of LabQuest at bottom of post). As I rode the elevator up and down, the LabQuest was recording my apparent weight (think about how you feel when an elevator first starts moving up or down, your weight seems to change).
I made five round trips, three recording my own weight, then two recording the weight of my Timbuk2 bag (I noticed I was bouncing quite a bit on the ride, and thought my bag might bounce less).
If you have Vernier LoggerPro software (worth the price for their video analysis even if you don’t have any of their sensors), you can download and work with the file. Here it is:
I did some data processing in this file; feel free to use it or delete it if you want your students to have to do it all themselves. The graph above was created by dividing the force on the scale by the initial (resting) force, then subtracting one to the the relative change in apparent weight. The maximum and minimum are both about 0.12g, or about 12% of gravity.
One discovery I found interesting is that the elevator does not have a continuous acceleration as it gets to its maximum speed, but rather starts with a high acceleration, then decreases its acceleration until it gets to its highest speed. When slowing down, it does the reverse: It starts with a low acceleration, increasing it as it slows until it comes to a stop and stops its acceleration (non-physics geeks: in physics, we don’t use the word “deceleration,” but rather just use positive and negative to tell direction).
I rode up the “express” elevator to the restaurant on the top. The security manager pointed me in that direction once I told him I was just wanting to collect the data for my classroom, not that I wanted to bring a bunch of high school students up with me. The express elevator turned out to be the best option, since I was able to see the maximum acceleration without having to stop at intermediate floors.