Showing posts from January, 2016

Acceleration of gravity

Laboratory three investigated the acceleration of gravity using timing of a falling time. Drop distances were 0, 100, 200, 300, 400, and 500 cm. Students are instructed to make five drops at each height and use the median value. This continues to produce better results than the original 2007 format for the laboratory with single drops every 20 cm. That the data produced a line similar to the acceleration curve generated on Monday, the half arc, helped, as noted last term. Pedagogically the linear acceleration (without the deceleration and resulting parabola on a time versus distance graph) works better for the material this week. Wednesday is then spent showing how velocity is changing in the Monday data and the resulting acceleration. Wednesday now needs some work: there is an opportunity in there somewhere to break up the students into groups and have them engage in a more exploratory approach to determining the velocity changes along the curve. A more inquiry oriented approach.


RipStik linear acceleration

Although this demonstration went well last term, this term my acceleration was uneven and my timing was off. Not having any sidewalk chalk left was a factor in making hitting the timing marks, but I also just was not able to get a good smooth acceleration this term.

I began as I did last term from the post at the sidewalk junction, running times off of 100, 200, 300, 400, 600, and 800 centimeters.

The unsteady line of travel probably did not help, and seeing the marks was problematic.

I actually made multiple runs, having to redo a run when a student I was using as the 800 cm reference point moved.

With time winding down, I went with a run that felt uneven in its acceleration.

Data was shared in the field.

The raw data from the final acceleration run. An analysis of the data confirmed that my acceleration had been very uneven, and my timing also appears to be have been in error.

time(s)distance(cm)velocity (cm/s)acceleration (cm/s²)000520.971001031062.0920089-122.83300135623.82400101-3…

Monilophytes, Lycophytes: Seedless Vascular Plants Walk

I began with a moss plant from the east end of campus that had sporophytic spore capsules present, doing that presentation in front of A101. Then I took the class west to the old Community College of Micronesia seal in the lawn which is now sporting Nostoc on top of the cement seal.

From there we walked west to the western field. I was caught off guard by the lack of Lycodiella cernua with cones, someone had harvested out essentially all of the L. cernua and Dicranopteris linearis for stage decorations. Time to find a new location with specimens.

In a positive development there are now more ferns than ever at the top of the hill, including a new Angiopteris evecta. The many Sphaeropteris nigricans atop the hill now means that the only fern in the valley is the Antrophyum callifolium. With one student pregnant and all other ferns present atop the ridge, I chose not to descend into the valley.

There is now both an Asplenium laserpitiifolium and another fern that is similar atop the rid…

Linear motion of a rolling ball

Last fall I shifted to using multiple chronographs in laboratory two, an exploration of the relationship between slope and speed for a moving ball. Although this shift increased the necessary equipment, the change also allowed students to work in smaller groups recording data.

Bee Hartly Siba with the new data recording table
I also shifted from the procedure of calling out times and having students note where the ball was at a particular time. Although this made time the independent variable, and distance the measured dependent variable, there was always an issue with the first second being longer than the other seconds. Years of trying to find way to minimize this error never yielded fruit. For some reason premarking distances and measuring time to the distance marks generates a more linear result. Probably in part by shortening the duration over which measurements occur. All curves look flat over short enough distances.

A new fiberglass tape measure reel permits measurements of up …

RipStik linear motion and walking speed

On Monday I began the unit by asking the class to name words that they associated with the word "motion". This led to "walk, slow motion, time, distance, speed" in about that order. I added the word pace. I asked if there was a relationship between time and distance for a moving object. I did not provide definitions nor equations. I only asked. Then I suggested that we gather data to determine whether there was a relationship. I used a new fiberglass outdoor long tape on a hand cranked spool. This gave me 2500 centimeters to play with. I then, as usual, rode my RipStik timing distances every 300 cm except the final 2500 centimeter distance.

time (s)distance (cm)speedacc00213.37501.3830021732.66600234134.03900219-115.281200240176.71500211-208.07180021969.592100197-1411.942500170-11
My speed fell slightly along the route, especially in the final 400 cm, but overall my speed was about as steady as I tend to produce on the RipStik. Coasting is not an option over a twent…

Banana patch gardening

The second day of ethnobotany class was rearranged to begin in the A204 computer laboratory. I used the computer laboratory to remind students to sign into Schoology and to show a series of videos on machete use and safety. The final video in the playlist is included as an example of how not to swing a machete.

After a video introduction to machete safety, the class walked down to the banana patch. I carried the machetes down in my car. This avoided having 27 students with machetes marching across the middle of the campus. I also passed out the under-development banana patch handout.

Kerat Esechu
At the end of the class I collected the machetes and loaded them back into my car, again avoiding carrying machetes across campus.

Sebastian Yinnifel

Casan-Jenae Joab

Unknown bananas, not uhten Ruhk. Suspected of being a more recent introduction or possibly uhten kirenis.
Uhten ruhk.

Density of Soap

The fall term began with a laboratory that introduces measurement through the measurement of the density of soap.

I began the laboratory with the Freeman Dyson quote:
For a physicist mathematics is not just a tool by means of which phenomena can be calculated, it is the main source of concepts and principles by means of which new theories can be created... ...equations are quite miraculous in a certain way. ... the fact that nature talks mathematics, I find it miraculous. ... I spent my early days calculating very, very precisely how electrons ought to behave. Well, then somebody went into the laboratory and the electron knew the answer. The electron somehow knew it had to resonate at that frequency which I calculated. So that, to me, is something at the basic level we don't understand. Why is nature mathematical? But there's no doubt it's true. And, of course, that was the basis of Einstein's faith. I mean, Einstein talked that mathematical language and found out that n…