Acceleration of a RipStik

Prior to the RipStik start at LRC I demonstrated that a true zero start was not physically possible. Friction with the wheels and the lack of sufficient slope prevent rolling from zero velocity. This demonstration helped me focus on low speed balance and was good preparation for the run. 


A slight nudge was used and then split times were taken at 1.5, 3, 6, 9, 12, 15, 18, 21, 24, and 27 meters. No active swizzling was done prior to nine meters. Last spring marks were at every 1.5 meters, this term the 1.5 meter marks had been erased by rain. This necessitated the remarking of the three meter marks. This choice of a single 1.5 meter mark and then 3 meter marks with no acceleration until 9 meters worked better than expected. 

The Desmos file was rebuilt with the expected distance marks, facilitating the data entry in the field.


After class the spring term Desmos was duplicated and enhanced with the inclusion of acceleration values per segment. Note the first acceleration value is the same as the second.


The data fit well to a parabola, and the climb in velocity was remarkably steady. In the field data was displayed only to 24 meters. After class the time at 27 meters, which was known to be slower than 21 to 24 meters, was added back in.


The acceleration was more modest than spring 2025 which had been 0.2291 meters per second squared. The slower the steady acceleration, the more evident that the shape is parabolic. 

Monday board borrowed only the graph to show student predictions of steady acceleration on a time versus distance graph for a RipStik.


The class remained in the field for the wrap up, including using the sidewalk as a white board.

Wednesday the full parabola was demonstrated. The sidewalk was completely remarked off of a new zero at the base of the slope. Marks at two, four, five, six, 6.5, and seven meters were made based on a practice run that suggested ten meters was a mark too far to be hit this term.


The turn was out around 6.5 meters, the time was interpolated.

Desmos

The usual issue of "leg linearity" can still be seen in the two legs, but the curve is better than the 3 meters marks. The timing works - but requires a couple practice runs to get used to the timing.

https://www.desmos.com/calculator/flko2brqfk


The velocity shows an unsteady decrease. 


On Wednesday the class returned to the classroom for the data analysis and wrap up explanation. 





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