Today I made a submission to an instructional video contest/program called EDU Guru, sponsored by YouTube, Google, and KhanAcademy (sorry... not gonna link those). Being somewhat of an instructional video skeptic, I tried to use this as an opportunity to illustrate the value of a genre of instructional video that would be less at odds with inquiry instruction. The video I submitted is here:
I've called it a VideoLab in conversations with friends. My hope is to create quite a few more of them this year. The relationship depicted here, of course, is less central to most introductory physics courses. We generally ignore air resistance precisely because it's messy, as the uncertainty in these measurements shows2. But I think it's actually pretty remarkable how even a system as gnarly and variable as this one can fit a simple model (as long as you give yourself some healthy error bars). In any case, the model of an "instructional video" that contains everything you need for collecting and analyzing quantitative data on a relationship could be quite powerful. It's no substitute for hands-on work, of course, but students who wouldn't otherwise have access to a proper physics lab (or simply missed class on lab day) could benefit greatly. Imagine if a whole slew of VideoLabs were accessible online... How 'bout it, folks? #videolab?
There's at least one precedent for using video this way, in the wealth of videos created and hosted by Rutgers Graduate School of Education (where I am currently a student!). Each of the videos on this site is designed to serve as part of a cycle in which students observe a phenomenon, form a hypothesis that explains what they've seen, consider the implications that their hypothesis might have for further observable data, then make a "testing observation" to see whether what's depicted in the video agrees with the prediction they made. The video I've made here is similar, but my goal is more to present students with data that can be analyzed quantitatively, in a style similar to the analysis of data collected during a paradigm lab of a Modeling Instruction unit.
1 65 mph check video here!
2 I also did the same experiment with a flat disk instead of a plastic bag (a cd, as you can see from the picture above), but it's a lot less fun to watch and the numbers are no less messy. I'm planning on editing that together too though, for comparison's sake, when I get a moment.
Joe,
I love this. You take drag forces out of the simple coffee filters world and give your students (and us) some real high speed drag force data to work with. I wonder if it would also be possible to design a set of slings with a known areas (made out of foam core), and then use them to get some info on how the area affects the drag force as well.
Thanks, John!! I was actually able to get measurable data with my fan at home while testing it out, so it may even be possible to a similar experiment in the classroom. The footage I have for a cd is a start, since it least gets the comparison conversation started. I'll try to get it up on YouTube soon!
Thinking about it now, it'd be neat to carry out that comparison with common objects that have a consistent area that students could measure themselves. A cd, an lp, the bottom of a coffee can. Or, just doing a direct comparison of two objects with the same projected area but different shapes could start an interesting conversation, I don't know if these results are precise enough to see that difference, but I'd love to try it out!
Joe,
I like all these ideas—I wonder if nailing down the area relationship can be enough for students to then figure out the cross sectional area of various things, like a falling skydiver (if we know the terminal velocity), or even the falling coffee filters that we use so often in the regular labs to determine the drag force. This would lead to some interesting questions about why the measured cross sectional area isn't equal to the are aof the botom of the coffee filter alone.
At our "Physics Teachers NYC" monthly workshop, I was just told about a set of videolabs made by a high school teacher named Peter Bohacek called "Direct Measurement Videos," hosted by Carleton College here: http://serc.carleton.edu/sp/library/direct_measurement_video/index.html
The videos are AMAZING!! Very high-quality, and detailed enough to contain any information the viewer needs to analyze the contents of the video quantitatively. This is exactly the kind of resource that I was trying to describe above, something that can expanding continuously as more and more teachers contribute. Wow!!!
In some ways I wish I had not seen this. Now I have all these ideas of things I hope to be doing with the free time I don't have. What a tease. Joe, great job!