This year, we’re teaching a new Computer Science 3 course for students who have completed the AP computer science exam. We started the year by having students complete a design crash course modified from Mount Vernon Presbyterian School’s flashlab, this time with a focus on reimagining the transition to a new school. We got some great ideas, including a room designer that lets roommates collaborate on how their room should be setup before arriving on campus, and a story web—an app that lets each member of the community tell his or her story and connect it to the rest of the community. Here’s what the prototype looked like:
AP Physics 2 started class sharing their mathematical models for pressure vs. depth below the surface of a fluid. In general, students struggled a surprising amount getting the equation for the best-fit line correct and handling unit conversions. One student shared that they needed a week to get back in the swing of things (it is the eighth day of class), and another shared that them struggling with this was “kind of sad.” Once we got the mathematical models captured in the Google Doc correctly, I was surprised at the range of values for the slope.
We discussed potential sources of major systematic error such as losing the seal between the glass tube and the plastic tube or heating up the air trapped in the plastic tube by holding it tightly throughout the experiment. I need to investigate calibrating the pressure sensors and seeing if the experimental technique can be improved to gather higher quality data.
After discussion the lab, we derived the general form of the equation through application of the balanced force particle model on a cylinder of water at rest within a beaker of water. It was good to reinforce a basic model from last year.
##paradigmlab ##setbacks ##expdesign ##fluids
Today in AP Physics 2, groups shared their results from yesterday’s fluid paradigm lab. The groups investigating pressure vs. volume of fluid above a point or pressure vs. depth in fluid were confident that the pressure at a point depended on the depth below the surface of the fluid and not on the volume of fluid above that point. They had sufficient data that they were also confident that there was a linear relationship between pressure and depth. The groups that investigated pressure vs. fluid density at constant depth/volume had inconclusive results. The pressure they measured varied by less than 1% between the three types of fluids. This provided an opportunity to discuss how the experimental technique can affect the uncertainty of the measurement. We discussed that with the new understanding of the relationship between pressure and depth, these groups could gather several measurements at various depths in each of the three fluids and compare the slopes of the resulting graphs to see if density has an effect. While we were discussing measurement uncertainty, we also discussed how the depth is defined not by the position of the bottom of the glass tube, but the water level within the glass tube. While the groups investigating the effect of fluid density on pressure applied their new experimental technique, the rest of the groups repeated gathering pressure vs. depth data while carefully examining the fluid level in the glass tube.
For homework yesterday, I posted a link to the four-step Plotly tutorial on linear fits. All students were able to create graphs in Plotly. However, what confused several groups was that Plotly reports the equation of the line of best fit as y = a + bx, and these groups assumed the coefficients were in the form of y = ax + b. That lead to some confusing results at first.
Some groups are still finalizing their analysis, but three groups in one class reported their findings for the mathematical model of pressure vs. depth for tap water. We need to work on units (check out the units on the vertical intercept) and investigate the cause of the error in the third equation (at least they have the proper units for their intercept).
##paradigmlab ##fluids ##chromebooks ##plotly
Today we started the AP Physics 2 fluids unit watching this video of a can being crushed as it descends in a lake. Like any paradigm lab, students made observations and enumerated variables that may be related to the crushing of the can. We determined which we could control and measure in the lab, and defined the purpose:
To graphically and mathematically model the relationship between pressure, volume of fluid above, depth below surface of fluid, and type of fluid (density).
We divided these various experiments among the lab groups, and groups started designing their particular experiment.
One group investigated if fluids of different densities result in different pressures at the same depth:
Another group investigated the affect on depth below the surface on the pressure.
Tomorrow, groups will share their qualitative results and then we will focus on refining our procedures to build the model while minimizing uncertainty. I love how students often surprise you in a paradigm lab when they focus on the characteristic that doesn’t affect the dependent variable. I can’t wait for the discussion after the group who measured the pressure in various sized containers with the same volume of water above the probe (which results in different depths for different containers) presents.
This paradigm lab was inspired by the article Pressure Beneath the Surface of a Fluid: Measuring the Correct Depth in The Physics Teacher.
I started AP Physics 2 today with the following on the screen.
I explained that we can’t afford to lose any more TAs as casualties of Scantron exams. So, we will be taking parts of our exams on our Chromebooks using Canvas quizzes. Everything went smooth. The new features related to specify when and how often students can see their responses and the answers will make it easier to keep control of the questions and yet review them in class.
##tech ##chromebooks ##canvas