This is a measurement of the downward acceleration of WTC 7 using Tracker, which is a free, open source program, part of the Open Source Physics project.
In discussing my measurement of the freefall of Building 7 with one (reluctant) physics professor, the professor at one point protested, “I’ll take your word for it, for the sake of argument, but I have no way to confirm your claims for myself.”
That comment astounded me because I see the motion of the building as such a straightforward measurement. But upon reflection I recalled all the time and energy and collaboration that went into gathering all the necessary materials and information for the measurement: a suitable video for measurement, an appropriate software tool to make measurements on the video, calibration data, knowledge of video formats, frame rates, etc. I realized that even with the requisite knowledge base and skill set, it would take a very motivated person to reproduce my measurements. I therefore have collected together all the bits and pieces that went into my measurements and present them here as a kit that can be used by a physics teacher or handed to a motivated physics student as a lab assignment or project or science fair entry. The skills that will be learned in the process will serve a physics student well for other projects that might involve using video as a measuring tool.
All the tools and material needed are free and downloadable here:
- Lab Instructions,
- the “Kit” with the necessary materials, (*Updated 3/18/2023)
- a link to the excellent measurement tool Tracker
- a link to a Video Tutorial on Using Tracker (search for other tutorials as well)
There is nothing particularly difficult in this measurement, but some familiarity with the concepts is necessary to understand the significance of the results.
Since not everyone has taken highschool physics, I have now gone one step further. I taught physics and math for over 35 years until my retirement, and since that time I have been recording the entire highschool math curriculum for self-teaching students, whether homeschoolers or adults returning to “fill in the gaps” in their background. Over the last couple of years I have added a physics course to the list. The complete course is available here, along with math courses from Algebra 1 through Calculus.
However to meet the needs of the physics-interested public who would like to better understand the events of 9/11 I have packaged a 5-chapter subset of that course and am making it available as “Physics for 9/11,” for download at no cost. It can be downloaded here. This subset of the curriculum covers measurement, motion, forces, energy, and momentum. (If you really get into it you might want to take the whole course, but this part is free.)
As I explained to one professor, what I have done is a straightforward measurement of a publicly observable event in the public sphere that is sufficiently anomalous to arouse anyone’s curiosity. Observing and measuring what is before your eyes is not political and should not be seen as controversial. This should be legitimate fare for students at any school or college, public or private. Deciding to NOT observe and/or NOT measure something and/or to criticize someone for making a measurement because of the feared political ramifications of the result, is in fact a political statement.
[I would be very interested to hear from any teachers or students using these resources for labs, projects, science fairs, etc. — David Chandler]
