The first day of school is in the books!
AP Physics: Bowling Balls
This concept development sequence comes from conversations with Michael Lerner, Kelly O’Shea, and the rest of the Physics! PLC!
I’m starting the year with momentum, so the first idea I want students to build is the impulse-momentum theorem. Today, we started with a version of Frank Noschese’s bowling ball & mallets activity. For the first time, when I asked students to whiteboard the pattern or rule they’d found, I had multiple groups write out the classic wording of Newton’s 3rd Law. These groups struggled to connect their statement to the lab, but still resisted changing their whiteboard because they knew their statement was true. I think this happened because we don’t have the class culture yet for every student to feel comfortable taking an intellectual risk. Tomorrow, I want to spend some time on the difference between true statements and useful statements to push some of those students away from quoting textbooks.
We’re starting the year with a unit on experimental design and graph interpretation based around a series of labs. For the first one, students are graphing mass vs. volume for some dowels. Things went well overall, but I should have spent a little more time on how to find the volume; I just told them to find it, and a lot of groups weren’t ready to make that leap on their own the first day of school.
Chemistry Essentials: Steel Wool
Students started the mass and change lab from the chemistry Modeling Instruction curriculum. To make the histogram, I had each group write their change on a Post-It, then place it in a physical bin matching their value before I transferred the Post-Its to the whiteboard. The balances were acting up, so most groups saw pretty big changes.
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.
AP Physics: Elevators
I showed students a video I made riding the elevator with a balance and asked them to determine whether the elevator was going up or going down and support their answer with free-body diagrams. I was pleased with how many groups started their conversation with “What’s our system?” I could tell from the conversations that a lot of students are still not entirely solid on the idea that an acceleration can be in the opposite direction of the motion, but thinking about the bowling ball lab from a few days ago seems to be helping. Next year, I want to do a better job of using the change in velocity arrows that show up in Etkina to help solidify the direction of acceleration.
Earth Science: Turbine Interference
In the next step towards designing a wind farm, students experimented with several turbines, comparing the amperage produced with different arrangements. This lab got my students asking some great questions that had me wishing that the trimester on physics came first rather than second this year. A lot wanted to know why the last turbine in a line wasn’t spinning, which is easy to explain with conservation of energy. A few others wanted to know what’s inside the turbine, which fits great with the build-a-motor lab we do in 9th grade physics. When we work on next year’s schedule, I’ll make sure to advocate for physics-earth-earth rather than this year’s earth-physics-earth sequence.
AP Physics: Defining Systems
We played the mistakes game with yesterday’s free-body diagrams. In both my hours, there was some great discussion about a problem with a skydiver attached to a parachute and whether the upward force should be a tension force from the straps of the parachute or a normal force from the air on the parachute, which lead beautifully into the importance of defining your system.
Earth Science: Topography & Wind
As the next stage of their project to plan a wind farm, students built a simple “topography” using textbooks and used simple flags to make observations about how that impacted wind speeds. Afterwards, students tried placing a turbine at some of the locations where they’d left flags and measuring the current produced.
AP Physics: Free-Body Diagrams
I gave a short lecture on the types of forces, then had students work on drawing some free-body diagrams. I’m being really picky about including the interaction when labeling forces this year (i.e. Fg (Earth on object)) which I’m hoping will pay off in deciding whether a force should be there as well as with the 3rd law. There were some great conversations about which forces need to be accounted for as well as what causes an object to move forward after the force is done.
Earth Science: Wind Maps
Students used some maps to look for a relationship between average wind speeds and topography. Then, they picked what locations in Minnesota might make sense for a wind farm. This lead to some good conversations about trade-offs in engineering, such as why there are some wind farms near big cities, even in parts of the state with relatively slow average wind speeds.
AP Physics: Bowling Balls
Students did a lab I borrowed from Frank Noschese hitting bowling balls with rubber mallets to look for a relationship between force and acceleration. I really like the conversations that happen when students are working out how to get a bowling ball to move at a constant velocity. When one group was wondering how to check, we ended up pulling out the Motion Shot app to make a motion map. Another group decided they needed to use gentle forward taps to maintain the constant velocity combined with even gentler backwards taps to counteract the forward ones; as they made their taps gentler and gentler, they eventually realized they could do away with them entirely. My 4th hour also got very excited about balancing things on their bowling balls.
Earth Science: Problem Scoping
On Thursday, students only had time to answer the problem scoping questions individually. Today, I had them answer the questions with their lab groups using a different colored pencil to differentiate individual ideas from group ideas. After that, we discussed as a class what kinds of things students will need to know for the engineering design challenge, which lead nicely into introducing and previewing the learning targets for the unit.
Physical Science: Building Again
Students spent today building the second version of their projects based on yesterday’s design. While students worked, I visited each group to grill them on how they’d used Newton’s Laws to decide on an effective design as well as the specific ways the prototype had influenced their new design.
Physics: Net Force
Students practiced some more free-body diagrams, this time also finding the net force. This included some problems finding the normal force exerted on a person in an elevator. Since my students finished quicker than I expected, I pulled up a force vs. time graph I’d saved after bringing a force sensor for a ride on our elevator, then asked my students to decide whether the elevator was moving up or down. I got really excited when I asked for a vote, and the class was pretty evenly split, thinking there may be some good debate. The first student to volunteer their explanation, however, gave such an eloquent and complete justification that no one wanted to argue with her. Fortunately, she was right 🙂
Did I take the elevator up or down?
Physical Science: Planning Tests
We did some debrief on last week’s testing of the engineering design challenge. Students agreed that the single ramp test was pretty limited, so, after getting new groups, students began planning new tests that would simulate a wider variety of real-world situations. The main constraints are that the tests must be reasonable to conduct in the classroom and they will need to provide evidence on the effectiveness of the design.
Physics: Bowling Ball Lab
We began building the balanced force model today. Students hit bowling balls with rubber mallets in a lab based on Frank Noschese’s 180 blog. Some groups were debating whether the bowling ball rolled at a constant speed when it wasn’t being tapped, so we fired up Motion Shot to check.
Bowling ball in Motion Shot
Students looked for a pattern in their motion maps and put a statement of that pattern onto whiteboards. The statements most groups started with had some exceptions or ambiguities, but by discussing these, we were able to generate a single statement the whole class could agree on.
One group’s statement of the pattern
Physical Science: Inertia
After some brief notes on inertia, students did a lab where they played with some examples and practiced using inertia to explain their observations. At the end of the lab, students had a mini-design challenge to come up with a way to keep the passenger safe in a collision. Even though we don’t go into torque in the course, it did get students thinking about where the force is applied. I intentionally left the language in the question vague, and I was pleased with the conversations students had about what it meant to keep the passenger safe.
This group debated about the efficacy of their “seat belt” since the passenger’s “feet” still swung forward in the crash
Physics: Introducing Free Fall
We went to the computer lab for students to use a Direct Measurement Video to begin exploring free fall. This one allows students to watch side by side high speed videos of a variety of objects in free fall. I asked students to find a value for the acceleration of a falling object and to identify any variables that affects that acceleration. While many students were quick to dismiss small differences in the time, one group had a great discussion. They saw that the bowling ball fell noticeably faster than a ping pong ball, so they not surprisingly decided that weight must matter. One person wasn’t satisfied; he played the video of a large steel ball side by side with a small steel ball to show they fell at the same rate in spite of different masses and radii. With some nudging, they were able to agree that density must be the key factor.