Science 9 – My science 9 classes built a paper model of DNA, with the phosphate, sugar and base pairs coloured in holiday colours. One of the parts of reproduction I’ve emphasized so far is the idea that DNA makes up chromosomes, sections of chromosomes make up genes, and genes code for proteins. As part of this process, RNA are small pieces of code that exit the nucleus. I jokingly turned our cutting of the DNA model (which has a copper wire structure) into an analogy of making RNA, where the RNA exits the nucleur pore (the classroom door). Each student had to cut a piece of DNA and carry it out to the garbage bin outside the classroom. Happy Holidays Everyone!
Robotics / Engineering – Much to my surprise, we’ve had problems consistently getting kids to come out to the robotics club. We have 3 full sets of Vex IQ robots, along with 10 sets of 2wd chassis robots with Arduinos. However, today there was a good turnout which was nice to see.
It was also great to see the kids destroy an LED! I’m not sure if they had it wired with the wrong polarity, or if they just didn’t have a large enough resistor on their circuit. Regardless, it’s a great way for kids to learn something about circuits. They all laughed pretty hard, so it will be memorable.
Physics 11 – Today we finally debriefed the lab results. There wasn’t a lot to say at this point because we had spent so much time talking about things just to get here. I really wish I could see how other modellers handle this kind of thing, I wonder what their whiteboard meetings look like?
A few things I would do next year, if I do this again:
- Force all groups to graph F vs a. While we agreed that a vs F made more sense with acceleration being the input, the analysis for realizing a general model from this is not obvious. By graphing F vs a, it’s easier to see that the slope is the system mass
- Have each group explicitly write down their system mass in kg while collecting data.
- Have a clearer discussion on how Fg = Fnet. I mentioned it, but I don’t think it resonated with the students.
Would I do this lab again?
There are three major problems with this lab. First, it took a heck of a long time. Second, not all the kids seemed to get the big picture. They got some data, calculated numbers that Mr. Smith told them to, and graphed them like Mr. Smith told them to. Some kids don’t fully appreciate the thought they put into their work. When they ask me questions like “what do I graph?”, I’ll answer with things like “well, what relationship are you trying to find? What should you graph? What should your independent variable be?”
My last statement above highlights the third problem. If they kids graph a vs F, which makes sense, then there is no obvious physical explanation for the slope. I have to explicitly tell them to change their equation to a =… (why?) or to purposely graph F vs a.
On the positive side, 2 of my 3 classes categorically thought the lab was good and recommended for next year’s class to do it. Several kids did have a solid A ha! moment, which is always good. Others said that playing with the video and analyzing the data made them appreciate how forces have a direct affect on acceleration.
I wonder if a more qualitative lab could replace this one? Something like what Josh Gates wrote about in the Physics Teacher (2014). I currently can not do exactly what he does because I don’t have the sensors, but it could be something to aim for.
Gates, J. (2014). Experimentally Building a Qualitative Understanding of Newton’s Second Law. The Physics Teacher
(9), 542–545. http://doi.org/10.1119/1.4902198
Science 8 – Today I tried to conduct a Socratic Seminar based on the above reading. This is taken from the Science Times website, which has a good selection of thought provoking science articles that written for different reading levels. In this article I expected a flow of ideas from “this is great, now everyone gets a vaccine” which eventually drives towards more critical thinking and ideas such as “what if you can’t eat yogurt” or “how do you know if you’ve had the right amount of yogurt?”.
The really hard part is trying to get 29 kids to have the discussion. The conversation gets dominated by 1/2 dozen kids, with about 1/2 the class doing everything they can to not participate.
One thing I would do differently next time is to assign the reading the day before, and maybe even administer a “Reading Quiz” to check for some basic understanding of the article before the Socratic Seminar.
Physics 11 – It was a long road, but today the students finally finished their unbalanced forces lab analysis. This took a lot more time than I had expected, and I would say that the work ethic has been pretty good. Lots of kids were getting a bit mixed up with their data and calculations, so there were several times where I would grab their data tables and quickly calculate acceleration and graph in Excel. I had thought about showing kids how to use Excel, Desmos or Plotly, but opted to stick with pencil and paper. Learning to use this kind of software would take another day of time. Heck, I even find Plotly and Desmos confusing at times.
I’m really wondering if it is worth all of this time to do a lab on unbalanced forces….
Science 8 – Students continued to work on their short stories and presentations. It’s amazing just how much use I can get out of my classroom notebooks. They are a fantastic tool to have on hand, it’s a shame they are not found in more classrooms. It’s also too bad that so many students have a $600 smartphone instead of a $500 notebook computer.
Physics 11 – Having become familiar with DMV for direct measurement, today I had the students analyze unbalanced forces as a substitute for the modified Atwood machine lab. The modified Atwood machine poses a few obstacles for understanding. First, it’s kind of hard to set up unless you have several sets of cart tracks and pulleys (we don’t). You also have to instruct students to keep the system mass the same (hand waving). You also need some decent technology to for measuring time and position (ie motion sensors or motion encoders), or your results go a bit sideways. I think ticker tape timers work quite ok for this type of lab, but only if the students have played and experimented with the timers before.
This year I wanted another try at doing the unbalanced forces lab so I went the direct measurement video path. The lab instructions were posted as seen above, and I introduced the DMV to them. To my surprise, many students continued to have problems finding the acceleration of the cart, they started collecting all sorts of data about position and time. We worked through it and by the end of the class all the groups had data, some groups had calculated acceleration and Fnet for each case, and some students even started graphing.