RipStik in Physical Science: Linear Velocity

To demonstrate linear motion while retaining some modicum of attention span from my social media saturated students, I again rode a RipStik along the sidewalk in front of the laboratory. The activity is built around the linear relationship between time and distance for an object moving at a constant velocity. Thus my goal was to retain a constant velocity over the 36.8 meter distance.


In class I only wrote the time and distance data on the board, the following table was constructed later as part of my analysis of whether my speed was fairly constant. 


Pillar Time (s) Dist (m) Vel (cm/s) Acc (cm/s²)
one 0 0

two 3.86 4.6 1.19
three 6.89 9.2 1.52 0.11
four 9.64 13.8 1.67 0.06
five 12.45 18.4 1.64 -0.01
six 15.09 23 1.74 0.04
seven 17.84 27.6 1.67 -0.03
eight 20.47 32.2 1.75 0.03
nine 23.45 36.8 1.54 -0.07

A constant swizzle rate tends to generate acceleration early in the run, and I could feel the increase in the speed between pillars one and three. I started the run prior to pillar one, but only by about three meters, so I had not yet reached a constant speed as I passed pillar one.

During the summer I opted to delay the stopwatch start until the second pillar to provide a seven meter run prior to starting measurements, . This fall I returned to starting with the first pillar as zero. The small variations in speed are visually difficult to see and thus do not impact the finding of linearity for the system.

 

At the very end of the run I usually run off onto the asphalt walkway. A visitor to campus from Japan was standing in that location, so I had to stop swizzling and jump off immediately after the last column. The visitor had a somewhat bewildered expression on his face as I hurdled towards him.


The small increase in velocity among the first three pillars and the deceleration at the run's end can be seen above. Mid-run my speed held fairly steady, accelerations remained near zero. The overall average speed for the run was 1.57 m/s, with the linear regression best fit slope at 1.61 m/s.

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

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

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