Day 104: Missing Energy & Designs

February 21, 2017July 14, 2017 / Marta R. Stoeckel / Leave a comment

AP Physics: Missing Energy

After watching a bouncy ball to see it loses mechanical energy, I tasked students with determining whether the energy is mostly dissipated during an impact with the table or mostly dissipated by air resistance. Today, they recorded video of the bouncy ball, then whiteboarded some representations for each explanation to get ideas about what could make good evidence. This is the first year I’ve done this activity where almost no groups think air resistance is the biggest factor. Students had a lot of great dialogue about forces and the motion of the bouncy ball as they worked on the representations.

Physical Science: First-Round Designs

Students worked on their first design for a cargo carrier that will protect an egg in a head-on crash. I don’t want this project to become just building, so I had students fill in a graphic organizer version of a CER, replacing the claim with their design idea and using the evidence and reasoning to explain why they think their idea will work. Tomorrow, I’ll help them make those explanations deeper by talking to each group while they build.

plan

Day 103: Energy Practical & Explanations

February 17, 2017July 14, 2017 / Marta R. Stoeckel / Leave a comment

AP Physics: Energy Practical

I tried a new lab practical for energy in an effort to integrate rotation and spiral back to some old ideas. Back in December, students measured the launch velocity of a marble, then predicted where it would hit the floor. Today, I had them use conservation of energy, including rotational kinetic energy, to find the launch velocity of their marble, then predict where it would hit the floor. I saw a lot of students pull out their old work, including their lab from December, to help remind themselves how to do the projectile portion of the problem, which is exactly what I hoped they would do. I overheard several students talking about how much they liked looking at an old problem through a new lens, as well as seeing how old ideas fit with the new ones.

Physical Science: Explanations

Students practiced making predictions and writing explanations using Newton’s Laws. I showed students some videos and clips, including one from Smarter Every Day and an animation of the Mars Pathfinder landing, then had them write an explanation individually, followed by a revised explanation with their whole group. I was struggling more than usual to keep my students focused, but part of the problem might have been the English test next hour and the pep fest this afternoon. I’ve got some demos I’m planning to have students write explanations of as warm-ups, and I probably would have been better off using the demos today, then using the videos as warm-ups.

newton

Day 102: Gallery Walk & 2nd Law

February 16, 2017July 14, 2017 / Marta R. Stoeckel / Leave a comment

AP Physics: Gallery Walk

I ended up having students do a gallery walk for yesterday’s problems.

wb-2

Physical Science: Newton’s 2nd Law

Students worked on a version of the modified Atwood’s machine lab for Newton’s 2nd Law. While I have students make a graph, we don’t go much deeper than whether each relationship is direct or indirect. I spent more time on the pre-lab discussion today than I have for most labs with this group, and I feel like that paid off with more confidence while they were actually working in the lab.

n2l

Day 101: Conservation & 1st Law

February 15, 2017July 14, 2017 / Marta R. Stoeckel / Leave a comment

AP Physics: Conservation Problems

I left my AP classes to chaperone a field trip, so they worked on some conservation of energy problems. I’m not sure how I want to go over the problems yet; based on what I saw in class yesterday, they are pretty solid on making bar charts, but are a little shaky on connecting them to specific quantities. I might do the mistakes game, focusing on setting up the equations.

Physical Science: 1st Law

Students did a lab based on various tricks using Newton’s 1st Law where they focused on writing good explanations of WHY the trick worked. For conceptual development, I don’t like this as much as the bowling ball and mallet lab I do in physics, but I like that they get a chance to practice explaining things using Newton’s Laws, which is important in helping them connect the science to the upcoming engineering project. Next year, I might try to add a day to this unit so we can do some version of both.

Day 100: Rotational Energy & Weight

February 14, 2017July 14, 2017 / Marta R. Stoeckel / Leave a comment

AP Physics: Rotational Energy

Students whiteboarded yesterday’s problems and we spent some time discussing how changing the system changes the LOL diagram. I picked a problem where a block on a spring becomes an upward projectile and a second where a block is launched by a spring up a track; I really liked using this pair since it drives home that path is irrelevant in conservation of energy.

Afterward, I had students use conservation of energy to predict the velocity of a marble at the bottom of a ramp, then we measured with photogates. Their prediction was off by about 60%, which I used as motivation to introduce rotational kinetic energy to account for the “missing” energy at the bottom. When students saw the actual velocity, they were quick to attribute the difference to friction, even after seeing the percent difference, so now I’m wondering if there are other good ways to rule out friction. Maybe time the marble down the track, then compare the acceleration to the component of gravity along the track?

marble

Physical Science: Weight vs. Mass

Students weighed hanging masses on spring scales to find a relationship between weight and mass. We moved this to the start of the unit since its the one thing we do with forces that doesn’t fit with our engineering project, but I feel like weight ended up separated from other important ideas from forces. As we dig more deeply into forces this week, I’ll make sure I circle back to the concepts of weight and mass, so I may decide this sequence was okay after all.

weight

Day 97: Energy & Free Fall

February 9, 2017July 14, 2017 / Marta R. Stoeckel / Leave a comment

AP Physics: Energy

We had a board meeting on the two energy labs from this week. The kinetic energy groups tended to get very nice results; I had them check their model with multiple cart masses and ramp angles, and they saw the results were consistent. I had the elastic energy groups use multiple springs, but they didn’t see as clear a difference between the slopes as I would have liked. I’m wondering if the results would be less muddy if I had them plot gravitational potential energy on one axis rather than just plotting height. I shortchanged some of the pre-lab discussion, and I think that lead to students forgetting to do things like measure the cart’s starting height or measure both the starting and ending height from the same end of the cart.

Physical Science: Free Fall

I got out washers, manila folders, and a few other things and tasked students with determining what affects the time an object takes to fall. In the pre-lab discussion, a student suggested the fluid an object falls through could affect the time, so next year I might make sure I have graduated cylinders and some different liquids available. I offered to grab materials if a group wanted to try that, but I think asking me to get stuff felt like an extra hurdle.

free-fall

Day 79: Whiteboarding & Snakey Springs

January 12, 2017July 14, 2017 / Marta R. Stoeckel / Leave a comment

I spaced out and didn’t take any pictures today.

AP Physics: Whiteboarding

Students worked on whiteboarding elements of the two problems they worked on yesterday. One of the problems involved a block that slides up a ramp and became a projectile; students were either nailing the projectile portion, or completely lost. With an AP test looming, I need to remember to keep spiraling those old concepts back.

Physical Science: Snakey Springs

Students made standing waves and looked for a pattern in how many wavelengths “fit” on the spring. I found a lot of groups missed some of the standing waves, so we made a list as a class of the number of wavelengths they could make a standing wave with and students quickly recognized the pattern.

We also talked a little bit about assessments. After the magnetism quiz yesterday, a lot of students told me they thought it hadn’t gone well, but the most vocal students had perfect scores and the class average was 85%. After talking to students, I think this is related to my challenges engaging students this tri. The earth science assessments they took 1st tri put a lot of emphasis on factual recall, so the reasoning questions I shoot for are big shift for students. I need to think about how I can make it less intimidating to face a new scenario and need to take some time to think on the test.

Day 78: Flying Pig & Quiz

January 11, 2017July 14, 2017 / Marta R. Stoeckel / Leave a comment

AP Physics: Flying Pig

Today, I got out the flying pig for a lab practical. I had students measure the length of the string and the height of the cone, then use what they know about forces and circular motion to predict the time for the pig to make 10 revolutions.

pig

Physical Science: Quiz

Students took a quiz on magnetism. Afterward, we took a few minutes to review vocabulary for talking about waves that students learned during first trimester. It was pretty teacher directed, but I didn’t want to spend much time on terms students should have mastered earlier this year.

Day 77: Friction on Ramps & Energy Sources

January 10, 2017July 14, 2017 / Marta R. Stoeckel / 1 Comment

AP Physics: Friction on Ramps

Students whiteboarded a few of the questions from yesterday’s activity examining motion graphs for a cart on a ramp. Usually, most of my students rotate their vector addition diagrams so that the legs of any right triangles are parallel to the edges of their paper. Today, I didn’t see any rotated diagrams; I don’t think its a coincidence that today was also the first time I saw students consistently make very strong connections to the physical situation they describe. Now I’ve got a chicken and egg question; did students leave the orientation of their diagrams because they saw the physical meaning, or did they see the physical meaning because they left the orientation?

I also had students write a CER on whether friction is negligible in the data I gave them. I ended up really liking how small the accelerations are; the acceleration when the cart is moving upward is only about 0.05 m/s/s larger than the acceleration when the cart is moving downward, but it works out to a 25% difference, so students had some great conversation about uncertainty and how big a difference is big enough to matter.

Physical Science: Energy Sources

Students signed up for a topic and started researching different energy sources for a short presentation. Minnesota has a standard about comparing and contrasting different energy sources, so I have them research the pros and cons of their energy source. I need to think about what I want to have students do when the are watching presentations at the end of the project.

Next year, I might introduce this project at the start of the electricity unit. I like connecting the energy sources to what students know about electromagnetism, but I think I can maintain that connection if I make the project due after the unit has ended. I always have at least some students without internet access at home, so I try to provide some in-class worktime for the project. Since I do several simulation labs during the electricity unit, I could build in some worktime by encouraging students who finish the lab early to work on their research.

Day 76: Unbalanced Forces & Motors

January 9, 2017July 14, 2017 / Marta R. Stoeckel / Leave a comment

AP Physics: Unbalanced Forces

I borrowed an activity from my AP Summer Institute where students get a position vs. time graph and a velocity vs. time graph for a cart on a ramp. At the institute, we were tasked with finding the angle of the ramp and force of friction, but I decided to take a more conceptual approach and tasked students with writing an argument on whether friction is negligible. This was a little ambitious for their first experience with 2D unbalanced forces; I think it would have gone smoother if we’d spent some time practicing free-body diagrams and vector-addition diagrams for unbalanced 2D forces first.

cart-on-ramp

Physical Science: Motors

Students built electric motors, then did some simple experiments to drive home the connection between electric currents and magnetic fields. They seemed to get the connection between today’s lab, the electromagnet lab from Friday, and basic electricity generation.

I also took some time during class to talk with my students about what I want from them during a post-lab discussion and what I’m trying to accomplish during those discussions. I saw a lot more students participating in today’s discussion, both by raising their hands and by adding to their notebook entries. I’m planning to keep reminding them of what the post-lab time should look like, as well as share a little more about why I do things differently than the other 9th grade teachers. I need to remind myself that even if I’ve been in this routine for a full trimester, this is still new to most of my students.