# Day 55: Toilet Paper Drop & Galaxy Sorting

AP Physics: Toilet Paper

Students started a lab practical I got from Frank Noschese’s blog. Students were given a height they will drop one toilet paper roll from and are tasked with figuring out where to drop an unrolling toilet paper roll so it hits the ground at the same time. I’m trying to emphasize the ways that students are using forces and constant acceleration in the practical to make sure this is doubling as a review for the final exam.

Earth Science: Galaxy Sorting

Students were given pictures of a dozen galaxies and tasked with putting them into categories and naming each category. Most groups came up with something pretty close to the three official categories. I can’t decide if I’m happy about that. On the upside, my students are very comfortable with the vocabulary. On the downside, the fact that so many groups got similar results tells me there was limited thinking required.

# Day 54: Rotational Inertia & Big Bang

AP Physics: Rotational Inertia

We finally collected data and prepped whiteboards for the rotational inertia lab we’ve been working on. Tomorrow, we’ll spend part of the hour on a short whiteboard meeting to figure out what rotational inertia is proportional to. Students did a nice job of working through all the calculations they had to do to get from something they could measure to the rotational inertia, and it was a good review for the final exam later this week.

Earth Science: Big Bang

We discussed the lab from last Wednesday, where students made a graph to find Hubble’s Law. In the discussion, we focused on this result as evidence for the expansion of the universe. Afterwards, I ended up lecturing on the Big Bang Theory and some of the other evidence supporting it. I’m rushing a little bit as I try to cram material in at the end of the tri. Today was a reminder that over the summer, I want to spend some time with the curriculum, comparing it to the required state standards and the district-approved learning targets to get a better idea of what I can cut and where I can add build in more time for scientific practices.

# Day 53: Rotational Inertia & Moving Galaxies

AP Physics: Rotational Inertia

Students took a quiz, then started working on a lab to find how mass and radius impact rotational inertia. A few students commented that they really liked the preparation I had them do yesterday, since they ended up with an outline of everything they need to do in the lab. Next year, I might provide a similar scaffold to some of the labs at the beginning of the year to help ease them in a little more.

Earth Science: Moving Galaxies

After some short notes on the Doppler Effect and its role in astronomy, students made a graph to show the relationship between the speed a galaxy is moving away from Earth with and its distance from Earth. With the break this week, students were a little less focused than usual, so we’ll spend some time on Monday discussing the questions that go with the graph.

# Day 52: Lab Planning & HR Diagrams

AP Physics: Lab Planning

Today, we started working on a lab to find how radius and mass affect the rotational inertia of a “T”. Due to some equipment conflicts, we’re using meter sticks and stopwatches, which means lots of calculations to get from the time it takes the mass to fall to the rotational inertia of the T, so we took today just to plan. I had students start by working backwards from the rotational inertia to the quantities they could measure for the falling mass and set up equations so they can just plug and chug during data collection. With finals next week, it worked out really nicely for students to have to go back to constant acceleration and unbalanced forces to make sense of the lab.

Earth Science: H-R Diagrams

Today, we focused on interpreting the H-R plots students made yesterday. I started by having students group the stars on their plot by type (giant, super giant, and main sequence), but held off on giving the names. I had students compare the giant stars to the main sequence, to see that the giants are brighter for a given temperature and asked them to come up with some hypotheses for why that is. This turned out to be much harder than I expected; I think the biggest problem is my students weren’t connecting absolute magnitude to any physical reality. Next year, I want to think about a bridging activity between the light intensity lab and this one to give magnitude some physical reality. It may also help to spend some time on the connection between the size of a light source and its magnitude.

# Day 51: CER & HR Diagrams

AP Physics: CER

Students practiced using the CER format to explain their answers on some TIPERs questions related to centripetal force and torque. Students are overall getting better at answering these kinds of questions, but many of them get stuck putting their process into words when they were able to use a formula to guide their answer. We only discussed one problem as a class, so I’m thinking about using a peer review process to go over some of the others.

Earth Science: HR Diagrams

Students worked on plotting temperature vs. absolute magnitude on a logarithmic grid to produce an H-R diagram. The plotting was much more time-consuming than I expected, partly because it was challenging for students to make sense of the logarithmic scale. I don’t think the time spent graphing did much to support understanding the science, so next year I want to give students a completed H-R diagram, then we can spend time making meaning, rather than making the graph.

# Day 50: Extending Torque & Light Intensity

AP Physics: Extending Torque

We had a board meeting to discuss yesterday’s lab with second class levers. On the lab, I simply asked whether the model we’d developed so far for a balanced lever also worked for this new type. Since the question is a bit ambiguous, groups that got similar results disagreed on whether the answer should be yes or no, which lead to some great discussion on what are the key elements of the model. I was also pleased with the way students talked about uncertainty to decide whether or not they could ignore the intercept. Over all, I’m really excited about how discussions with this group are going. I feel like I’m getting to take more of a backseat and listen to students talk to each other, rather than relying on me to guide the conversation.

Earth Science: Light Intensity

Students graphed the diameter of a light beam vs. the distance from a light source, making some qualitative observations about brightness along the way. We used the results as the basis of a discussion about why an astronomer would want a big telescope to observe very distant objects. I also did some having students observe the pen light itself from different distances to get across the idea that, even though the light beam spreads out, the light source doesn’t look any bigger.

# Day 49: Extending Torque & Sun Layers

AP Physics: More Torque

After formalizing the results of yesterday’s lab, I showed students a second class lever and asked them to decide whether the model we have for torque applies to these new levers and prepare a CER on a whiteboard. Most students went back to the first lever lab, where we looked for a relationship between the two forces and got beautiful results, including an intercept that’s too big to ignore. I was pleased at how many groups immediately decided to measure how much force it took to balance the lever with no additional weight on it and by how many had good conversations in their lab groups about what must be causing the intercept.

Earth Science: Layers of the Sun

Students used the textbook to complete a jigsaw on the layers of the Sun. The textbook has a line about “bright hydrogen lines”, so we had some good discussion as a class about how to interpret that statement and connecting back to the spectroscope lab we did a few days ago.

# Day 48: Torque & Lenses

AP Physics: Torque

Students found a relationship between the distances masses had to be at on a lever in order to balance. Using two different masses, they picked a spot to place one mass, then moved the other until the lever balanced. Data collection went quick enough that we also had time to whiteboard and discuss the combined results of this lab and yesterday’s lab comparing forces on either side of a lever. I was pleased at how quickly students picked up the ratio hidden in the slope of each graph. I’m also continuing to take more of a background role in the discussions as students get more skilled and comfortable at talking physics.

Earth Science: Lenses

Today, we added refracting telescopes to our repertoire of astronomy observing tools. Students started by making observations through lenses of different focal lengths individually, then both simultaneously. My students are getting better at picking up on little observations, like distortions at the edges of the lends, or asking interesting questions, like whether the image will always be upside down with two lenses, and I’m getting better at responding with the question “How could you find out?”

# Day 47: Torque & Spectra

AP Physics: Torque

Students started the classic lever lab to start building some ideas about torque, though we haven’t used the term yet. Today, I had them work on a relationship between the forces on either side of the lever, and encouraged different groups to use different distances from the fulcrum.

Earth Science: Spectra

To introduce why spectroscopes are useful in astronomy, students played with diffraction gratings. We started by looking at some of the regular light sources in the classroom, and they were quick to come up with interesting observations and ideas to explain their observations. Then, we shifted to observing gas lamps. We only have one power supply, so we did those observations as a whole class. Then, in their lab groups, I had students look for patterns in where colors appear to get the idea that the same color always has the same distance, then to try to identify the gasses we’d observed.

# Day 46: Mistakes Game & Reflecting Telescopes

AP Physics: Mistakes Game

We played Kelly O’Shea’s Mistakes Game using some problems with a central net force. Its great to see my students getting more skilled at discussing physics, which means I’m doing very little to keep the conversation moving. We had some particularly good discussions about a problem about the forces on a roller coaster car as it goes over a hill and about the forces on a yo-yo as it swings in a vertical circle.

A whiteboard for the roller coaster problem

Earth Science: Reflecting Telescopes

Students played with curved mirrors to get some ideas about how mirrors are used in telescopes. I also got out some electric candles and tasked students with projecting the candle on a sheet of paper. They struggled with that step, but it was great to see their reactions when they got a nice, sharp image of the candle “flame”.