RipStik acceleration

In a previous article I shared the use of a RipStik in SC 130 Physical Science to demonstrate linear constant velocity motion. The ability to generate a relatively constant velocity by swizzling at a constant rate on level ground was useful to that demonstration.

This term, as in the past two terms, the non-linear motion of the rolling ball in laboratory two had already set up the concept of curved lines as changing speeds on a time versus distance xy scattergraph. This permitted me to move directly to data gathering for an accelerating RipStik.


I did not achieve the top end that I typically attain, I am uncertain as to why. Prior to class I performed three practice runs with a goal of first pillar-to-pillar time of six to seven seconds. The hope was to hit an acceleration around 0.2 m/s².


My actual run during class suggests an actual acceleration of 0.068 m/s². The chart belows compares the desired accelertion curve against my actual acceleration curve. The time to the first pillar was right on the mark, but my acceleration fell to nearly zero.


A more careful examination of my pillar to pillar velocity indicates that my acceleration was low until the final two pillars.


Raw data:

 
Time (s) Desired (m) Practice run 1 (m) Practice run 2 (m) Practice run 3 (m) Actual run (m) Actual v (m/s) Actual a (m/s²)
0 0





6.8 4.6





9.6 9.2





11.7 13.8





13.6 18.4





15.2 23





0
0




7.78
4.6




13.16
9.2




16.8
13.8




19.37
18.4




21.91
23




23.62
27.6




0

0



5.69

4.6



9.59

9.2



12

13.8



14.22

18.4



16.75

23



0


0


7


4.6


11.27


9.2


14.53


13.8


17.54


18.4


19.06


23


0



0 0 0
7.22



4.6 0.64 0.09
13.13



9.2 0.78 0.02
17.06



13.8 1.17 0.10
20.16



18.4 1.48 0.10
21.91



23 2.63 0.65


Acceleration started off well below the desired 0.2 m/s² and remained below this value until the final two posts. Average acceleration was only 0.12 m/s². The approach of rolling as slowly as possible into the first pillar - essentially a zero acceleration after the initial push-start - in order to clock seven seconds to the second pillar, appears problematic.

I think the idea of a continuously increasing beat remains the most likely approach to producing a constant acceleration. This is likely, however, to cause me to hit my maximum speed sooner.

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