I spent the day working with my district’s science curriculum team. We are working on deepening our understanding of the Next Generation Science Standards and how they will influence the design of our K-12 curriculum. I spent most of the day analyzing the performance standard: “Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.” and connecting it to the Science and Engineering Practices, Disciplinary Core Ideas, and Crosscutting Concepts. Personally, I can only understand something at so deep a level based just on reading about it. Today, we had the opportunity to analyze, discuss, and apply these concepts. I’m beginning to gain a deeper understanding of the design of the NGSS.
Today we did one of my favorite labs in AP Physics B. Students measured the mass of an electron. They placed a vacuum tube in a solenoid to deflect the electron path. They measured the current through the solenoid, the accelerating voltage of the vacuum tube, and the radius of curvature of the electron path. They derived the necessary equations to relate these three variables to the mass of the electron. They use different sized dowels and corks to measure the radius of curvature which isn’t very precise, but we usually are within one or two orders of magnitude of the actual mass.
Here is the experimental setup:
Here is the electron beam:
Huskie Robotics, FIRST Team 3061, is the the middle of the FIRST Robotics Competition build season (three weeks into the six week season). This is a very busy time. A week ago an extremely generous member of our community donated some tools and equipment to the team. Included in his donation was a string of bolt sizers, which our student mechanical lead is now wearing as a necklace. He needs all the help he can get as they try to assemble a three-motor shifting gearbox without any instructions!
Today we traveled to Libertyville High School for our first Science Olympiad competition of the season. The team did well and brought home many medals. They also learned what needs improvement before the regional competition. The coaches ran the Technical Problem Solving event, which consists of lab activities utilizing probes. In the past, this event required significant effort and materials to run (probes, LabPro, laptops). This year, we were able to use Vernier’s LabQuest 2. The event was the smoothest ever and all our materials fit in three boxes!
My AP Physics B students can play circuit sudoku and analyze fairly sophisticated DC circuits. Once I take away all the numbers and they have to reason through the problem conceptually, they are challenged. This is another example of where peer instruction can be effective. Students tend to favor analyzing circuits from a current model rather than a voltage model and, therefore, struggle with problems like this one:
As groups discussed this question, I heard the expected claim: “When the switch is closed, the current is now split between A and B; so, A will be dimmer.” The first part of this statement is true but not the second as the students are assuming constant current. After some discussion, students questioned each other enough to shift to the voltage model and realize that the potential difference across A would not change. Certainly a better use of class time than another circuit sudoku practice problem!
The whiteboard below is problem #16 in Chapter 19 of Giancoli Physics 5e. Of all the homework problems, students found this one the most challenging because they had to reason through it conceptually and couldn’t fall back on numbers and equations to provide the answer. The problem was the circuit as shown on the whiteboard and asked how the voltage and current associated with each resistor changed when the switch was opened. (It also asked about how the terminal voltage changed.) I like how this group captured their thought process and showed their long chain of reasoning.
The Huskie Robotics FIRST Robotics Team works four days a week. On Mondays, Wednesdays, and Thursdays we meet from after school until 9pm. That’s a long day and we are fortunate that parents volunteer to bring in dinner that they have cooked or purchased. The whole team sitting down together, taking a break, and sharing the successes and challenges of the day has become an essential part of our culture. We are fortunate to have such strong parental support. Tonight was pulled pork!
Today we started whiteboarding the first set of problems for the central force particle model unit. I’ve been very careful to focus on the net force applied to an object undergoing uniform circular motion and focus on the forces that result in an unbalanced force directed toward the center of the circle. Despite this, one group will present this whiteboard tomorrow:
They have added an additional force “Fc” to their free-body diagrams. It is interesting that this has appeared despite me never having used the abbreviation Fc. Regardless, it will result in a good discussion tomorrow.
Students started to finish their media computation collages today. The rest will be submitted throughout the weekend. I love the creativity and individuality that this lab provides. Great start to the semester before tackling ArrayList next week.
In AP Physics B, we spend a lot of time learning to visualize electric fields and equipotentials. One of the most helpful activities to develop this visualization is a lab where students map the electric potential on a grid of conductive paper and enter the results in an Excel spreadsheet that generates a 2D contour plot and a 3D surface plot. (This is the one time during the year we use Excel.) The 3D surface plot is particularly good at helping students visualize the electric field and equipotentials. We use a modified version of the spreadsheet that comes with the Advanced Physics with Vernier – Beyond Mechanics Lab Book
I believe this surface plot is of two concentric circles (high potential is the inner circle).