Physical Science: Electromagnets
Students built electromagnets and designed experiments to test the effect changing the number of coils has on the strength of the magnet. I also pulled out my homemade speaker for students to try out.
Physics: Mistakes Game
Students played the mistakes game with the diagrams for solving force problems. Once my students have their diagrams, they can get through the problems pretty easily, so I wanted them to focus on drawing and interpreting those diagrams.
Physical Science: Magnetic Fields
My students have gotten really good at looking at new content in terms of energy, so I put together an assignment to compare topographic maps as a measure of gravitational potential to magnetic field lines as a measure of magnetic potential. The assignment needs some revisions, but I like the basic premise and my students definitely understand magnetic field lines much better than my students have in the past.
Physics: 2D Forces
A lot of students were on a field trip yesterday, so we used whiteboard speed dating to go over yesterday’s problems. Based on what I saw and heard, students have these problems down better than they give themselves credit for. I’m thinking about how I can adjust my plans tomorrow to help students feel more confident with the material without resorting to me doing an example at the board.
Physical Science: Magnetic Fields
To introduce magnetic fields, I had students play around with a bar magnet, some filings, and a compass. Several groups were really fascinated by the compass, and there was a lot of discussion about why the north indicator on the compass go would to the south pole of the magnet. I also decided we need to revisit forces tomorrow. A group noticed that the magnet made some of the filings stand straight up and was trying to figure out why, which was great! The problem is the best why they could come up with is “magnets break gravity.” I’m pretty sure students just don’t have the idea of balanced forces well enough to come up with the idea that the magnet must exert a force to balance gravity.
“Magnets break gravity”
Physics: Vector Addition
After yesterday’s practice drawing vector addition diagrams, students combined the diagrams with calculations to solve more traditional word problems. I gave them a few goal-less problems, which simply describe a situation without asking for anything in particular. My students don’t have a lot of experience with these (at least not yet!), but I like the way they encourage students to play with models to see what they can come up with, rather than getting fixated on the right answer. They really reinforce physics as a creative, sometimes playful, process.
Physical Science: Kirchoff’s Rules
With my 9th graders, I’ve always done series and parallel circuits pretty superficially where they try a few things in the lab, then memorize a couple of key behaviors. This year, my students have been thinking about the energy in circuits in some interesting ways that seem useful for getting at Kirchoff’s Rules, so I decided to give it a go. Today, students used PhET’s circuit kit to compare the voltage and current in different parts of each type of circuit. Students were able to articulate very nicely their own versions of Kirchoff’s Rules based on the energy in the circuit.
Physics: Vector Addition Diagrams
Today, students took their first look at forces in 2D and drew some vector addition diagrams to scale. The problems, lifted from Kelly O’Shea, were all on a grid to keep things straightforward. This gave students the opportunity to practice drawing vector addition diagrams and start thinking about what they mean without getting bogged down in the math. Tomorrow, we’ll start crunching numbers with the diagrams.
Physical Science: Electric Power
Students plugged several different light bulbs into Kill A Watt meters to find the power used by each, then calculated how much you’d pay for the electricity to use each one for a year. This is the first year I’ve done energy before electricity with my 9th graders, so I decided to have them sketch energy bar charts for each light bulb, using thermal energy and light as the energy types. For the first time, my students had an easy time articulating in a meaningful way why the low wattage LED was just as bright as the high wattage incandescent.
Physics: Unbalanced Force Problems
Students worked on some problems that combined Newton’s 2nd Law with constant acceleration calculations. I was a little nervous, because they just got Fnet = ma yesterday and many are still mastering net force, so I wasn’t sure how they’d do with using multiple models on a single problem. However, a lot of pieces seemed to really click today. By the end of the hour, several students who’ve been struggling with constant acceleration declared today’s problems easy, including the portions where they had to do constant acceleration calculations.
Physical Science: Series vs. Parallel Circuits
Students used PhET’s circuit construction kit to explore the differences between series and parallel circuits. When I’ve used batteries and bulbs, students really struggle to see (let alone articulate) what’s going on with the current, so the visible “electrons” in the simulation were a huge help in getting students to understand why certain changes happened.
Physics: Board Meeting
We discussed as a class the results of the Newton’s 2nd Law lab. I need to have students practice talking about the slope more; they were able to get to “The force needed to accelerate 1 m/s2“, but it took some pushing on my part; I think the issue is just lack of practice. I was pleased by the discussion; students are doing more articulating of the big ideas. I was really excited by the discussion students had about the intercept. I’d planned to declare the intercept zero and move on, but in both sections students seemed interested in talking about it. They decided it would be reasonable to have a non-zero intercept on this experiment and it would be equal to the amount of friction you have to overcome to start the cart moving.
Physical Science: Presentation
Students delivered a presentation on the engineering projects they tested last week. They were asked to provide an overview of their design, their thinking behind it, and the results of their testing, linking back to Newton’s Laws to explain why things did (or didn’t) work. The presentation is meant to convince the project’s imaginary customer to develop their design into an actual product. I need to keep revising how I approach the presentation. I’d like to use it as an assessment over Newton’s Laws, and students make some great connections between the project and the science content, but as soon as they get to the presentation, those connections seem to disappear.
Physics: Newton’s 2nd Law
Students finished data collection and graphing for their Newton’s 2nd Law lab. The netbook cart I reserved actually worked, which meant students saw the advantages of graphing in the classroom. Several groups had a point that looked like an outlier, and their question was usually “Can we grab a track to check that point?” rather than “Can we ignore that point?” I like the first question a lot better.
Physical Science: Ohm’s Law
I gave students some batteries, some light bulbs, and some wires and asked them to find a qualitative relationship between resistance and current. Groups that had some extra time decided to experiment with voltage, as well.
Physics: Interactions
Students worked through some questions that reinforce the idea of forces as interactions between two objects from the Modeling Instruction curriculum. I was out of the classroom for a field trip, so I’ll find out how it went tomorrow when we discuss some of the answers.
Physical Science: Light the Bulb
I gave students a light bulb, a battery, an assortment of conductors and insulators, and instructions to figure out how to light up the bulb. As usual, a lot of students were quick to declare it would be easy because they did the same lab in elementary school. That confidence quickly fades once they get into the lab; I think a lot of students learned the trick without understanding why it works. Tomorrow, I’ll probably take a few minutes to show a clip of fresh MIT graduates struggling with the same task.
Physics: Newton’s 2nd Law Lab
Students started data collection on Newton’s 2nd Law. A few groups wanted to try using a spring scale to apply a constant, known force to their cart, but ended up deciding the classic modified Atwoods machine would be easier. I’ve only got four LabQuests, so my students’ only exposure so far has been demonstrations and class discussions. I was very pleased when a couple of groups in each section asked if they could use a LabQuest and motion detector for their data collection, in spite of their lack of first-hand experience with the devices.
Physical Science: Van de Graaff Generator
After sharing and discussing observations from yesterday’s lab, we played with the Van de Graaff generator. I like to end with sending a shock through a chain of students, then have two students hold onto an aluminum rod instead of holding hands. Students aren’t too surprised when they still get shocked with the rod in the chain. Next, I switch out the rod for a wooden meter stick and students aren’t too surprised when the shock stops at the meter stick, which provides a nice segue into conductors and insulators. This year, I also had students hold one of the rubber rods they’d used in their static electricity lab. Since it had been easy to give the rubber rod a static charge, students expected it to work at least as well as the metal rod. I’d tried this on a whim, and it ended up being a great reminder for me that students don’t easily differentiate between carrying a current and holding a static charge.
Physics: Newton’s 3rd Law
Students made free body diagrams for a variety of scenarios with two carts colliding, then predicted which cart would experience the greater force. After students had worked, we used a pair of force sensors to test their predictions. I’d also planned to show Frank Noschese’s great video of cart collisions, but ran out of time, so I’ll start with that on Monday. There were some great debates when students were working on their predictions, though students were more insistent than usual that I should step in and tell them who was right. This provided a good opportunity to talk with my classes about what we know is needed to really internalize a new concept, which helped alleviate some of the frustration with my non-answers.
Simultaneously Learning & Teaching
Ideas for Physics Teachers
explorations and inspirations... in how we learn science
Brian reflects on his physics teaching
(sometimes) daily updates about physics classes, mistakes, and sensemaking
Recording reflections about teaching and learning
Physics, Modeling Instruction, Educational Technology, and other stuff I find interesting
Reflections on the dynamics of teaching
Ever tried. Ever failed. No matter. Try again. Fail again. Fail better. - Samuel Beckett
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