# 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 11: Uncertainty, Buggies, & Norms

AP Physics: Uncertainty

We had a board meeting on yesterday’s force of gravity lab, and the discussion was better than I expected at this point in the year. As we were talking about the slope, one student claimed “Gravity doesn’t change”, which lead nicely into what we mean by that and how we know. In response, another student shared that yesterday one of her group members said “The force goes up 10 N for every 1 kg of mass”; after finally reading Arons this summer, one of my goals is to have students make “for every” statements about slope, and I was thrilled it came up naturally.

I also introduced uncertainty during the board meeting. Students had a lot of great observations about the relative precision of measurements and how much mass it took to change the reading on the scale, which gave them a sound conceptual basis. I rushed the discussion since the end of the hour was coming, and it ended up more teacher-directed than I’d like, but I’m pleased with how the basic approach worked.

Physics: Buggies

Students collected data for the buggy lab. Since when I ask for observations, there is usually a student who says the buggy is moving at a constant speed, I took a page from Michael Lerner and framed the lab as seeing how we can find out. A few groups are starting to make “for every” statements about their slope, which I did not see during the introductory unit and is great to see. I think the relationship is more obvious here than it was in the intro labs.

Chemistry Essentials: Norms

I’ve been struggling with classroom management. This is a very high-energy group, and there are a lot of things that are a lot of fun, but I’ve been having trouble keeping them on task and getting them to voices besides their own. I decided to pause today to spend some time developing norms as a class. I think a lot of students felt it was punitive, but many also agree that things aren’t working at the moment.

# Day 82: Board Meeting & Experimental Error

AP Physics: Board Meeting

Students whiteboarded their results from the cart explosion lab to start building the momentum transfer model. I can tell its been a while since we’ve done a true model-building lab, so students needed some reminders about how to linearize or “translate” y=mx+b, but those skills came back pretty quickly. I did wish I’d had students linearize a bigger variety of graphs so far this year; a lot of students went straight to squaring a variable, so I may want to think about how to get more variety early in the year next year.

When we discussed the lab, a few groups had linerized based on a quadratic relationship and had a fairly large intercept. To decide whether the large intercept made sense, one student suggested exploding the plunger cart off empty space to get a mass ratio of zero and show the velocity ratio must also be zero.

Physical Science: Experimental Error

We spent some time discussing yesterday’s speed of sound lab, focusing on error in measurements. I tried having students stand in different parts of the room based on how they thought frequency affects the speed of sound. When students were picking their spots, there was a lot of great conversation, including some contrasting frequency and speed, which was a great side effect. As we talked about error and what it means for values to be “close”, I had a lot of students ask to move because they changed their mind about what the answer should be.

# Day 12: Linearization & Heating

AP Physics: Linearization

Most students finished their position vs. time graphs, so we took some time to talk about linearization. I really like the ways that uncertainty played into the discussion. In particular, students were quick to recognize that the line of best fit doesn’t go through the error bars and that the intercept is much further from 0 than the uncertainty. This motivated nicely that, even though the line had a good r2 value, it wasn’t good enough.

Earth Science: Heating

Students placed thermometers at different angles in front of a lamp to simulate the sun striking the surface of the earth at different angles. I like that this lab starts with a question, namely  “Why is it hotter at the equator?” Next time, I’d like to involve students in more conversation about how we can model that in the lab since I think many lost the connection between the question and the data they were collecting.

# Day 3: Uncertainty & Ocean Currents

AP Physics: Uncertainty

I did a short lecture on uncertainty (I know, ugh, but I didn’t have any bright ideas for a better approach), then students figured out the uncertainty on their buggy lab measurements and prepped whiteboards. Tomorrow, as we dig deeper into the physical meaning of the graphs, we’ll translate the equations for the lines into physics-speak.

Earth Science: Ocean Currents

Students made some observations of a video of convection currents in a tank of water, then worked on combining those observations with a map of ocean temperatures and what they know about the Coriolis Effect to predict what the major ocean gyres should look like.

# Day 48: Experimental Error & TIPERs Projectiles

Physical Science: Experimental Error

Students calculated the speed of sound based on the data they collected yesterday, then compared that to the expected result. Students found the speed using five different tuning forks, so we had some discussion about what it meant for those two different speeds to be close enough to be considered the same, which lead to some good conversation about experimental errors and why the values varied.

Physics: TIPERs Projectile Questions

I picked some questions out of TIPERs to help get my students thinking conceptually about projectiles. I was surprised at how many students struggled with a certain question where a ball is thrown upwards at two different speeds, and a student in the problem predicts that the faster projectile will reach the highest point first. Once I prompted students to sketch velocity vs. time graphs, the question ended up being pretty easy. It was a good reminder for my students to look at what tools they have, even when the problem isn’t about a calculation.

The faster object reaches its highest point in more time!

Today’s quiz on projectiles launched horizontally also reminded me why I love standards-based grading. Several students have been really working on solving problems with constant velocity and constant acceleration, and finally showed mastery when they applied those skills to projectiles today. I loved being able to give them credit for all the skills they showed, not just the big idea on today’s quiz.