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RipStik wave and the speed of sound

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I attempted to introduce waves by riding my RipStik on the porch at the Kosrae campus main building. This would fail as the boards would be too smooth to leave behind a wheel track imprint from the RipStik. I moved over to the library where the sidewalk was not wet from the morning rain and promptly slid out on a remaining patch of wet sidewalk which had a thin layer of cyanobacteria on the sidewalk. That spill provided me a chance to discuss Newton's third law only operating when an opposing counterforce can be generated - the RipStik generates propulsive force via friction. No friction, no counterforce, and the board slides out. Newton's second law comes into operation: without a counterforce, my force on the board accelerates the mass of the board out from under me. A conservation of momentum moment occurs: the boards goes skittering farther than I do. Less mass. I then brought the paper and the class back to porch to continue the class. There I used the ...

Field trip to Leluh ruins to gather GPS data

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In an extended unit exploring latitude, longitude, tilt of the earth, solstices, equinoxes and possible astronomic alignments of ancient sites on Kosrae, the summer 2018 physical science class traveled to the prehistoric island capital of Leluh. Recent work by Richard, Shen, Hobbs, Wu, Jiang, and Beardsley (New Precise dates for the ancient and sacred coral pyramidal tombs of Leluh, 2015) date the oldest sections of tombs to circa 1310 A.D. Thus the city dates back to the 14 century and provides evidence of the existence of a nation state. Although the class is specifically interested in whether Leluh aligns Finol Finkol (the highest mountain in Kosrae) and Menka with the rising summer solstice sun and the setting winter solstice sun, a secondary interest was whether portions astronomical alignments might exist within Leluh. The class departed campus at 9:30 in two vehicles. Arriving at 9:55, the group was met by guide and Leluh Ruins association president Palik Sigrah. Th...