Author: Marta R. Stoeckel

Day 77: Friction on Ramps & Energy Sources

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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

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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.

 

Day 75: Whiteboarding & Electromagnets

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AP Physics: Whiteboarding

Most of my students were on a field trip today, so classes were pretty small. We whiteboarded some problems from earlier in the week on balanced forces in 2D. While the problems had a lot of calculations, I just had students whiteboard their diagrams and set-up, including some intentional mistakes. Later, I’ll post correct answers to the class website so students can check their calculations.

 

Physical Science: Electromagnets

Students built electromagnets, then made some observations about the magnetic field and strength of the magnet.To visualize the field, most groups opted for the compass over the filings, which reinforces my thinking earlier this week that I should start students with the compasses to see the bar magnet’s field.

This week, I’ve been thinking a lot about the fact that I’m really struggling to engage students the way I’d like, especially in post-lab discussions. The last couple of years, I’ve been able to get almost immediate buy-in from my 9th graders, but I think that’s because I only taught them during 1st trimester, when I got to set their expectations for high school science. Most of my students right now had a different teacher 1st tri, so I’m upending their expectations just when they were starting to get comfortable with high school and need to be much more intentional about helping students adjust. On Monday, I want to start with some conversation with the class about my observations and why I do things differently than their other science teachers. I’m also going to start thinking about how I can smooth the transition 3rd trimester, when about 2/3 of the class will be new to me again.

electromagnet

Day 74: Balanced Force Practical & Field Lines

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AP Physics: Balanced Forces Practical

I tasked students with figuring out the unknown masses in a set up with several strings at different angles. Groups found they had to be very clear about what they defined at their system, which as a nice element of the task. Different groups defined their systems differently and took different approaches to solving their vector addition diagrams, which lead to some fantastic conversations when groups who finished early compared results. I got really happy when I overhead a student slowing down his group down by telling them the process is more important than the answer, and even used the fact that I couldn’t remember the masses I used as evidence.

During prep today, I got a kick out of grading quizzes. I’ve been asking students this year to self-assess and do a short reflection on each quiz, and several students took that into specific problems on this quiz. These students wrote down some really interesting, specific metacognition right alongside their solutions without any extra prompting. It was really interesting to read. I might start having students do some journaling later this tri to explicitly encourage that kind of thinking.

practical-1

Physical Science: Field Lines

To help make sense of magnetic field lines, I had students connect gravitational energy to a topographic map of a hill, then went back to the magnetic field lines we saw yesterday to talk about magnetic energy. I haven’t done any forces with this class yet, but they are fairly solid on energy, so magnetic energy seemed to help ground the material in a way I don’t think forces would have. I also like that the topographic map helped link back to some of the map interpretation students did first tri in Earth Science.

field-lines

Day 73: Force Vector Addition & Magnets

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AP Physics: Force Vector Addition

Students worked some problems with balanced forces in two dimensions. We also had some discussion about whether you could have a mass hanging from a perfectly horizontal rope and used some hanging masses and string to experiment with some of the ideas. Not surprisingly, they really wanted it to work with a small enough mass in the center and a large enough force on either side, but once they started drawing free-body diagrams, it became very clear that the rope has to flex.

tension.jpg

Physical Science: Magnets

Students played with some bar magnets and steel filings to start building some ideas about magnetic fields. Every year, my 9th graders struggle to see patterns in the filings, even when they are very clear to me. I usually have them start with the filings, then get out a compass to compare the patterns. Next year, I might have them plot the orientations of a compass arrow first, giving them some specific positions around the magnet to check, then get out the filings. That should give them an idea of what to look for in the filings.

magnet

Day 72: Vector Addition & Electric Power

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AP Physics: Vector Addition

I shamelessly stole an activity that Casey Rutherford shared on Twitter. I gave students some free-body diagrams drawn to scale, and had them use pipe cleaners to rearrange the vectors and do some graphical vector addition. The activity not only reinforced graphical vector addition, but I was pleased with how it drove home the difference between forces that are balanced and forces that are equal.

vectors

Physical Science: Electric Power

Students plugged different light bulbs into Kill-A-Watt monitors to find the power each one used. To emphasize the connection to energy, I also had students sketch energy bar charts for each light bulb, using light and thermal energy as their energy types. This lead very nicely into a comparison of the efficiency of different light bulb types.

killawatt

Day 71: Quiz & Circuits

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Today was our last day of classes before break!

AP Physics: Quiz

Students took a quiz on projectile motion. My collaborative team’s goal is related to experimental design, to I included a problem to give my students some practice and feedback on designing on an experiment entirely on paper. I planned to have them play with some Mystery Tubes after the quiz, but it went longer than I expected, so I will save those for another day.

Physical Science: Circuits

I got out the light bulbs and batteries for students to build real-life circuits and see if the models they developed with the simulation still work. Not all of our light bulbs are identical, and I didn’t check the kits before class, so some groups had bulbs with different resistances. Next year, it could be interesting to use that as a feature, rather than a bug, and ask students to rank the resistance of their light bulbs based on qualitative observations.

circuit

Day 70: Hoop Practical & Circuits

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AP Physics: Hoop Practical

We finished up a lab practical on angled projectiles. Each group had a different distance from the launcher and figured out how high above the ground to place a hoop. In both classes, some groups had to shift their hoop to one side or the other, but eventually managed to get the projectile though all the hoops. I also had some goal-less problems to try and shift students away from needing to be able to picture the full solution to be able to progress. The problems mostly got ignored, because it was more exciting to watch the parabola of hoops come together and it took most of the hour to get all the hoops in place.practical

Physical Science: Series vs. Parallel Circuits

Students used the PhET circuit construction kit again, this time using a lab on series and parallel I modified from Eugenia Etkina’s PUM curriculum. I think students  were getting the big ideas, but its very tough to circulate with a full class in the computer lab, so I feel a little blind. Last year, I was able to do the PhET sims on netbooks in the classroom, so it was easy for me to listen i on student conversations and pull them together at the end of the hour to discuss some big ideas. Next year, I might re-work my calendar to make time for a day in the classroom so my students and I have a chance to make sure they are on track.

circuit

Day 69: Angled Projectile Practical & Ohm’s Law

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AP Physics: Angled Projectile Practical

We wrapped up yesterday’s mistakes game, then started a lab practical. Each group got a different distance from the launcher, and needs to determine how high off the ground to place a hoop so that the projectile will travel through it. Tomorrow, we’ll setup the hoops so students can see the results. In both this practical and the problems we’ve been doing, I’ve found some of my strongest students get stuck. They usually know what they’re doing, but don’t see their way to the answer yet. I need to keep reminding my students that they can play with the pieces, even if they don’t know what the full picture will look like yet. I might look for a good goal-less problem to combine with the practical tomorrow to help push them towards thinking about what else they can do, rather than what the answer must be.

launcher

Physical Science: Ohm’s Law

I’ve found I really like having students use PhET’s circuit construction kit before we get out the batteries and bulbs, so today we went to the computer lab to find a relationship between current, voltage, and resistance. I left the directions fairly open so that students would be designing their own experiments. Since I don’t talk much about units in this course, the simulations ammeter felt like a black box to a lot of the students. I was really intrigued by one student who measured current by counting how many blue dots passed a selected point in one minute, which connects really nicely to the definition of current as the flow of electric charge.ohms-law

Day 68: Mistakes Game & Light the Bulb

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AP Physics: Mistakes Game

My students LOVE using the mistakes game to go over problems (a few have even decided to sneak in mistakes when they whiteboard problems in calculus), but it doesn’t lend itself nicely to complicated calculations like projectiles. To get around that, I tried having students whiteboard just the set-up to Friday’s problems for the mistakes game. Students embraced it and we had some good discussions about the physics without getting bogged down in the algebra. Since students did not see full solutions to the problems during class, I posted the answers, along with my complete solution to one of the problems, on Google Classroom.

wb

The artist made sure I saw the person on the bottom floor (where they physics room is) is happy and focused, while the history student on the top floor is angry enough to throw a book

Physical Science: Light the Bulb

Students were given an assortment of materials and tasked with lighting a light bulb. Afterward, we watched a clip from Minds of Our Own of MIT graduates attempting the same task. Students were pretty successful at picking out some of the key ideas about what a circuit is. Tomorrow, we’re using the PhET circuit construction kit, and I’ll probably have them start with the same task in the sim to reinforce that a circuit is a closed path since its not obvious with the light bulb.

bulb-lab