RipStik wave and the speed of sound

In the morning I followed up on the weather station visit by demonstrating a dry and wet bulb thermometer. I then demonstrated using a table to determine the relative humidity, heat index, and relative health risk of that heat index. This was followed by making a RipStik wave on poster pad paper in front of the south faculty building.


As the class was seated to the east of the entrance to the building, I opted to lay down the sheets on this slope. I used an uphill run but my turn-around had been sketchy on the east side of the sheets. Wobbly, I came in a tad slow with low amplitude. The initial wave length was 30 cm on an amplitude of only 2 cm. I accelerated up sheet ending on a 60 cm wave length and a 7 cm amplitude. This complicated the analysis.


A student timed the run, I held and drank coffee while riding. The time was 1.75 seconds for what was crudely some 4.75 wavelengths laid down across 248 cm of poster paper. This put an average period at 0.37 seconds, a frequency of 2.71 Hertz, an average wavelength of 52 cm, and a wave speed of 143 cm/s.


Again I used cellular communications to handle the intermittent rain. Once one is out beyond 100 meters, shouting is not possible.

Hansha, Jason head west

John and Gino in the distance by the "B101" Pterocarpus indicus (Narra) tree.

The timer line up

Marsha flagging John. Mayleen, Shirley-Ann, Hansha, Marsha, Jason, Marlinda, Marmelyn, Sucy-ann, and Preston time or record data.

Reset and rerun.

Rain would move in after 200 meters. 250 meters was abandoned and 300 meters, at maintenance was the next stop. Above is roughly 400 meters.

450 meters

1476 feet. The 8 in the second digit would not clear. The wheel is increasingly balky about resetting.

Preston, Marsha, Marlinda, Jason at 450 meters

The long road back to John, Gino. Hard to believe but we could see them rather easily today. Cloudy weather works better than sunny weather. Hearing was easy too. There was a quietness to the campus, and a light easterly breeze was in a laminar flow across campus.


Data and results suggest a speed of sound only about 4 percent below the published value for today.

Comments

Post a Comment

Popular posts from this blog

Plotting polar coordinates in Desmos and a vector addition demonstrator

Image
In an earlier post I noted that Desmos did not directly plot polar coordinates. Not only was I incorrect, but Desmos responded to my blog to correct me! Although I had at some point seen that one could define a function f(x)=3x+5 and then have Desmos calculate f(6), I had not absorbed how this might be used to plot polar coordinates. The above works beautifully . Realizing that I could effectively program Desmos, I applied this thinking to demonstrating how to add two vectors when given the magnitudes m and the direction angles theta. The graph calculates the i and j components for the two vectors and then adds the vectors, graphically displaying the result while also providing information on the magnitude and direction of the vector sum. m1 and theta1 are the magnitude and direction angle for one of the two vectors, m2 and theta2 are the magnitude and direction for the other vector. All four are dynamically interactive and can be changed. The diagram purports to illustra...
Read more

Traditional food dishes of Micronesia

Image
Clara, Jennette, and Joanie presented ground hard taro cooked in an umw, effectively a hot rock oven. Pohnpeian: rotama. Pingelapese: sero. Mwoakillese: rodma. Mortlockese: Amahd. Kosrae: rodoma. After cooking in an umw the rotama is pounded with the petiole of a palm frond. Rotama is made from hard or swamp taro, known as mwahng on Pohnpei, mweian on Pingalap, pula in Mortlockese, and pahsruhk on Kosrae. In traditional times on the outer islands the women had primary responsibility for tending the taro while the men handled fishing and climbing tasks. Joesen and Noeleen presented fermented breadfruit from the outer islands of Yap such as Woleai and Eauripik. The raw ingredients were actually brought in from Yap, Noeleen prepared the maare.  The leaf wrap is ti leaf - Cordyline fruticosa. Pauleen, Barnson, Trisha, Verginia, Con-ray, and Maylanda from Kitti, Pohnpei brought in mahi umw, koahpnoair koakihr, and uht sukusuk. Above is breadfruit umw, mahi umw, o...
Read more

Setting up a boxplot chart in Google Sheets with multiple boxplots on a single chart

Image
The  Google Statistics  add-on for Google Sheets can display multiple boxplots in a single chart. The key is the layout of the data. One column should be the variable by which the data is to be grouped, the other column should be the data to be box plotted. Set up the Statistics add-on with the data to be plotted as the variable, and the grouping column as the "by" variable. In this image I had deselected all but the boxplot option, the result was the appearance of the Moment, Standard errors, and Confidence intervals options. The default is apparently a 95% confidence interval for the mean. The result is multiple boxplots on a single chart with a common scale. The new tab that is created also quotes 95% confidence intervals for the mean. Note that as of 2018 the Google Statistics add-on cannot be found by search in the add-ons. In addition, as of May 2018 the add-on no longer verifies, possibly due to the add-on not having been updated since August 2017. One may ha...
Read more