# Day 77: Friction on Ramps & Energy Sources

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

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.

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

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.

# Day 110: Motors & Half Life

Physics: Electric Motors

Students built simple electric motors, then experimented with how they could change the behavior of the motor. They drew a lot of nice connections between their observations and the previous work we’ve done on wires in magnetic fields. I let students use power supplies, and the sparks that showed up at higher voltages were very popular.

A student took this photo that’s way cooler than anything I got

Chemistry: Half Life

Students simulated radioactive decay using M & M’s, with one side representing the parent isotope and other representing the daughter. To reinforce half-life is based on probabilities, rather than hard and fast rules, I wanted to have students compare several runs of this experiment. Each group did the experiment twice, then submitted their averages to a Google Form. Tomorrow, we’ll look at the class data to see how it compares to the results of individual groups.

# Day 109: Wire Loops & Nuclear Reactions

Physics: Wire Loops

My plan was for students to experiment with interactions between two wire loops with currents running through them, but we were not able to get much to happen with two loops. Instead, we ended up using some YouTube videos of the experiment to make observations. Students did get good results observing interactions between the wire loops and a magnet. This lab did provide a nice opportunity to revisit a common misconception from last week’s quiz, where a lot of students struggled to identify how a charge at rest would respond to a magnetic field. We were able to use how a wire with no current running through it responded to revisit the idea that charges must be moving.

Chemistry: Nuclear Reactions

Students did some problems predicting the products of nuclear reactions. This year, I really emphasized applying a conceptual understanding of conservation of mass to balancing chemical reactions, and that provided a good foundation for nuclear reactions. Even though the elements involved were changing, students were nicely primed to think about these reactions in terms of conserving protons and neutrons instead of elements.

# Day 107: Wire in a B-Field & Hydrocarbons

I was chaperoning an AVID college visit today, so all my classes had subs.

Physics: Wire in a B-Field

Since we don’t have a current balance (and I haven’t had a chance to build one), I had students watch a YouTube video and work through some questions about the forces on the wire.

Chemistry: Hydrocabons

Students used the textbook to get an intro to some terms related to hydrocarbons and organic chemistry.

# Day 106: Whiteboarding & pH Lab

Physics: Whiteboarding

Students whiteboarded their solutions to yesterday’s problem. In my class of 15, I had students present while in my class of 35, I tried a gallery walk, instead. I really liked the gallery walk with the big class; it gets hard to hear from everyone with that many people in the room, so talking about each board in smaller groups made it possible for more students to both ask and answer questions.

Chemistry: pH Lab

Students did a lab to find the pH of household chemicals. Students did a nice job of connecting the properties of each chemical to the properties of acids and bases.

# Day 105: Magnetic Force Problems & Gallery Walk

Physics: Magnetic Force Problems

Students worked on some problems calculating the magnetic force on a current-carrying wire and a moving charge. Tomorrow, we’ll whiteboard the problems.

One of my students was eager to tell me about his visit to University of Minnesota-Duluth on Friday. He got a chance to hear from a physics professor about the use of inquiry, collaboration, and discovery learning in the physics courses, including why UMD takes that approach. The student was very excited to tell me UMD’s intro physics sounds just like my class, but with calculus, and that I must know what I’m doing if I’m teaching the same way as a professor. February and end of tri are always draining, so it was nice to get this boost from a student.

Chemistry: Gallery Walk

A lot of students in this class are very uncomfortable presenting whiteboards, so I decided to do a gallery walk. Each pair prepared a whiteboard of their solution to one of the problems and I checked their work. Then, one partner took their sheet and visited other whiteboards while the other partner stayed put to answer any questions on their solution. One student went above and beyond writing out the work for their solution, so her board was a very popular stop!

# Day 104: Electromagnets & Neutralization

Physics: Electromagnets

We finished Friday’s lab exploring electromagnets and students compared results. I had students look for as many ways as they could to change the properties of the field around the electromagnet. I was surprised to have several groups decide to try flipping the nail in their electromagnet to test what effect that had. I was glad they did, because it reinforced that the nail itself was not the source of the magnetism.

Chemistry: Neutralizaiton

I did some grade checks during class on Friday, so the students weren’t asking very many questions on the neutralization worksheet and, as a result, almost no one had gotten past the example I did on Friday. We spent some time revisiting how to write the equation for a neutralization reaction and students got some time to work.

# Day 103: Electromagnets & Neutralization

Physics: Electromagnets

Students built electromagnets, then started exploring to try and describe the shape and direction of the magnetic field and to find ways to affect the magnetic field. A lot of groups were quick to come up with tests to see if the electromagnets behave like bar magnets.

Chemistry: Neutralization

Students practiced writing equations for neutralization reactions and predicting the products. The biggest challenge was how many different ideas, including formula writing and balancing equations, they had to combine. My students got very good at both of those skills, but we didn’t use them much the last two weeks, and some students struggled to rediscover their previous fluency. I need to do a better job of spiraling some of these key concepts so that students don’t have the opportunity to get rusty.