# Day 11: Uncertainty, Problems, & More Problems

AP Physics 1: Uncertainty

We did a quick preview of tomorrow’s lab on impulse, then talked about the challenges of finding the uncertainty of measurements given the tools we have so far. This lead into Brad Wysocki’s measurement lab to take a look at uncertainty caused primarily by your measuring tool. In my 2nd hour, I asked groups to find the area of some index cards using each ruler, but the size of the cards lined up too nicely with the rulers and the main points weren’t as clear as I’d like. In my 4th hour, I switched to Post-Its and the uncertainty was much clearer.

Physics: CVPM Problems

Students started working problems using CVPM. The problem set started with several descriptions of motion and students had to determine which statements CVPM could apply to. That was a more challenging task than I expected, largely because a lot of students were not clear about what I meant by CVPM, so I need to work on keeping that language clear. I also found my 1st hour, that mostly worked individually on the last problems, very easily shifted to working in groups today while a had a lot of students in my 6th hour opting to work alone, even though most of them went into groups on their own last time.

Chemistry Essentials: Density Problems

We started by discussing the results of yesterday’s lab. I ended up projecting some data I collected rather than making whiteboards. When we were talking about whether measuring a bigger dowel would give a different density, student comments revealed some of the class was interpreting data points on my graph as dots in a particle diagram. I’m really excited that my students are looking for connections between the different representations and are willing to share their thinking, even if we have some work to do on distinguishing between those representations.

Afterward, students worked on some problems relating particle diagrams, mass vs. volume graphs, and density. A lot of students had trouble getting started because they were struggling with the vocabulary; I pretty quickly wished I’d put together a short vocabulary activity to reinforce terms before we got to work.

# Day 7: Dueling Buggies, Board Meeting, & Volume

AP Physics 1: Dueling Buggies

Students predicted where two buggies would collide based on their starting points and speeds. It was interesting to see how different sections approached this problem; most of the groups in my 2nd hour used motion maps while almost all of my 4th hour used position vs. time graphs. When my 4th hour discussed the buggy paradigm lab, students brought up the fact that some of the graphs intersected, with one even bringing up that position vs. time graphs can be used to elegantly solve the classic two trains problem.

Physics: Board Meeting

Students wrapped up the buggy lab and we had our board meeting. Before the board meeting, I once again had students do a gallery walk and jot some notes down on their lab sheet, which lead to some really good conversation during the board meeting. The downside is students are using the gallery walk to ask questions I’d normally hope to hear during the whole-class board meeting, like asking about what a group was doing when they collected data that gave a negative slope, but students bringing up those points during the whole-class phase, so it doesn’t feel like a big downside.

Chemistry Essentials: Volume

Today, students found a relationship between the amount of water displaced and a solid’s volume in cubic centimeters to get at the equivalence of milliLiters and cubic centimeters. I haven’t had great results with the Modeling Instruction volume lab, so this year I cut some rods from the metals teacher into short sections so that students only needed to find the volume of cylinders. I like that the lab I did today uses the same version of water displacement they’ll use later on, but the math was a struggle for a lot of students. About half of my groups finished data collection and the other half only got one data point because they were caught up calculating the volume. I need to keep working on how to make this lab accessible to all of my students.

# Day 28: Conservation of Momentum, Mistakes Game, & Measurement

AP Physics: Collisions

After their quiz, students wrapped up the data collection on the collisions lab. Things went very smoothly, and a lot of groups have already commented on the pattern in their momentums.  This is one of the times I love having quantitative uncertainty in the course, because students are independently deciding whether their momentums are close or effectively equal.

Physics: Mistakes Game

Students played the mistakes game with stacks of kinematic graphs. In class discussions, I’ve been struggling to get students to speak up and it is usually one or two students who do most of the talking after lots of long silences. Today, one of those students asked a question about the a vs. t graph, a member of the group presenting said, without any shame or fear, “We don’t really understand those graphs, so we just drew something.” All of the sudden, the whole class was animated and students who are normally quiet, even in small groups, were jumping in with fantastic questions. It was a fantastic way to end the week with that class.

Chemistry Essentials: Measurement

When I gave some notes on temperature scales yesterday, I had a student ask whether Kelvin is a more accurate scale than Fahrenheit and several others questioned it when I said 98.6 rounds to 100. I’m really excited about the thinking about measurement this shows, so I decided to lean in and do a Modeling Instruction measurement lab I’d skipped during the first unit. I had students measure the lab tables with popsicle sticks, gradually adding marks to make them more accurate. Next time, I think I will have them measure a bigger mix of objects, including some shorter than their tool.

# Day 10: Force of Gravity, Lab Practical, & Volume

AP Physics: Force of Gravity

Students collected data to plot the force of gravity on an object vs. its mass. I had different groups use spring scales with two different ranges. Tomorrow, I’ll use the different levels of precision to motivate a discussion of uncertainty. Groups with the 50 N spring scale have already noticed that the smallest hanging masses don’t noticeably change the scale’s reading, which is exactly the kind of observation I was hoping for.

Physics: Lab Practical

Students revisited the dowel lab, this time as a group assessment. Their results on the original lab weren’t as good as I was hoping, but they are looking much better now that students have had an opportunity to discuss the flaws in their original approach.

Chemistry Essentials: Volume

Students found the volume of several different shapes, then measured how much water was needed to fill each one. Some groups got beautiful results, but other groups struggled. I think the groups that struggled had trouble matching up their measurements to the formulas on the cheat sheet I gave them or the Google calculators I showed them. A lot of students also also had trouble measuring the amount of water they put into the shape. The groups that struggled with these measurements were also the groups that were the least focused, but I’m not quite sure which issue is the chicken and which is the egg.