RipStik Sine Wave Generator

As I did last spring and summer session, I opted to use the RipStik for the introduction to waves in SC 130 physical science. I used a modification of the set-up I deployed last spring. The new floor tile, which had an uneven surface, was an unknown factor last summer. I used a larger towel. I used red food dye and kneaded it into a wet rag towel. 

The red food color did not appear to stain the ceramic tile. The results were, as they had been in summer,  better than those in the spring. The first run above was 1.79 seconds for two sections of poster pad paper.

The second swizzle run, seen above, was 1.69 seconds for the two sheets of poster pad paper. Note that the towel is turned the long way relative to last summer. This worked, I had no traction issues either on the towel nor on the paper.

The tracks dried with the reddish tinge of the dye clearly visible once the papers were put up on the board. I did emphasize the lines using a white board marker so the students could see the lines better. I used the curves to introduce the concepts of crest, trough, wavelength, amplitude, frequency, and period to the class. I also introduced the more obscure and arcane terms sinusoidal propulsion and swizzle.

The two sheets were 165.5 cm in length. Using the 1.69 second run, my linear speed 97.9 cm/s. Last summer my velocity was 105 cm/s, hence term-to-term my speed is fairly consistent. The number of wavelengths on the paper was not so fortuitous at 4.75 wavelengths for the second run. The period was 0.356 seconds, and the frequency of the swizzle was 2.81 Hz. This was a slightly higher frequency than the 2.55 Hz of last summer. The mean wavelength was 34.8 cm, but the actual wavelength varied wave-to-wave. Multiplying the frequency by the wavelength yielded a wave speed of 97 cm/s. The amplitude was on the order of 3.25 cm - slightly smaller than last summer.

If nothing else I have the rapt attention of the class during this demonstration. The RipStik remains novel enough to the class.