Linear motion laboratory modifications

An instructor who once worked for many years at the college kept three by five cards with notes on each class he taught. After every class he would make a few notes on how the lesson went and then file the card in the appropriate place. The next term he would review the cards from prior terms, noting what had worked and what had not worked. This blog is my collection of three by five cards. I write for my future self, and rather expect that I might be the only reader.

Once the covered walkway was complete and the sidewalk between the LRC and the south faculty building was resurfaced, I moved the Monday RipStik run to that location. This location works better than the main walk between the administration building and the north faculty office. The only catch is that the Japanese solar panel pillars are metrically spaced while the covered walkway pillars are on a non-metric spacing. The covered walkway pillars are close to 305 centimeters center-to-center, except in certain locations where they vary for walkways junctions and building entry ways.

I chose to use a short run up from near the LRC and start timing near where the junction with the walk way that runs on the west side of the south faculty building occurs. I timed pillars down to where the spacing was no longer 305 centimeters near the main entrance to the south faculty building. There is one 320 cm span in the run which was ignored in the data below in order to simplify the demonstration. This worked rather well. There is ever so slight a drop in elevation which almost exactly offsets slowing.



The result is a very linear data set with a reasonable RipStik speed, for a 54 year old professor, of 214 cm/s.

Due to suspicion that the use of BlackBoard's CourseSites fall 2013 negatively impacted lab report turn in rates, this spring I planned on an additional day in the computer laboratory at term start to sort out technology issues. In prior terms only laboratory one and three have ended in the computer laboratory, spring 2014 labs one, two, and three all wrapped up in the computer laboratory. This would provide three days to get the students up to speed with Schoology.com.

The change in venue from the gym would prove fortuitous in a number of ways. One, the issue of switching the dependent and independent variables should be more obvious because the laboratory was done along the same stretch of sidewalk as the Monday RipStik run. Two, using Excel to graph the data would prove far more complicated than I expected. Excel 2010 takes the data to be row-wise instead of column-wise. Switching this requires accessing a right-click Data Select option and swapping the x and y values. Demonstrating this is necessary, there is no way to describe this convoluted action.

LibreOffice.org gets the data layout right from the get go, no need to swap anything. LibreOffice.org understands the first column to be the independent variable (as opposed to trying to use the first row). Apache OpenOffice 4.0.1 is a code sibling to LibreOffice, differing only in the use of semi-colons instead of commas in formulas. There are other subtle differences - in the chart module Apache appears to have more marker options than LibreOffice.


In the early morning the crew was a tad thin. At 8:00 just Reed Floyd and I. I bowled and marked one and two seconds with my zoris, Reed marked three and four seconds. As more students drifted in the crew expanded. Bowling is difficult in this location. The sidewalk is arched for drainage, and a cross-headwind was blowing from the northeast. 


A view to the east.


Data from the morning runs, constrained initially by the number of bodies available - two. The last run would have the most data collectors and would record distances of 0, 730, 1440, 1660, 1960, and 2180 centimeters respectively.

Apache OpenOffice 4.0.1

The session in the laboratory went the full three hours, both sections. Getting 022 set-up in Excel is a challenge, and then there was the technology assistance. I did find that Schoology's student driven merging of two accounts to be a straightforward and logical solution to this inevitable problem. College bandwidth constraints, however, made all Internet based work slow and prone to occasional timing out.

Note that the above system completely does away with the use of a ramp. Term after term, bowlers have proven capable of repeating a speed close enough for the spotters to be close to their second mark. The data still displays a "too fast" first second compared to the second second. Years of watching this laboratory have convinced me that the ball is not slowing down that appreciably between second one and two. Yes, the ball is slowing, but there is also a reaction time delay for the timer reacting to the ball crossing the 0 centimeter line.

Recommendation to self: keep the second half of labs one, two, and three in the computer laboratory. Run these labs on the east side of campus.

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