RipStik wave quiz

In order to set up a quiz problem for SC 130 Physical Science, a RipStik was ridden across a wet cloth towel soaked in water with blue food color. The RipStik was then swizzled across a large sheet of presentation paper. This had been demonstrated previously in class, thus the quiz was based on something the students had actually seen.
The RipStik traveled a distance d of 83 centimeters in a straight line in a time t of 1.3 seconds. The swizzle wave mark made by the wheel had a wavelength λ of 23.5 centimeters. The oscillation rate for the RipStik wheel was measured as 3.5 cycles in 1.3 seconds. The amplitude A of the swizzle mark was 3.25 centimeters.


The swizzle used is near the bottom of the paper. The marks represent four runs across the paper.

The students were then asked to answer the following questions:
  1. Calculate the linear velocity v for the RipStik.
  2. Calculate the frequency f for the RipStik wheel.
  3. Calculate the period τ in seconds for one oscillation of the RipStik wheel.
  4. Calculate the velocity of the swizzle wave based on the wavelength and frequency.
  5. Toughie: What is the name of the method of propulsion for a RipStik?
  6. Does there appear to be a connection between the answer to question one and the answer to question four ? If yes, what is the connection?
Note that the students were given the following formulas at the bottom of the quiz (among many other formulas):
d = ѵ t
τ = 1 ÷ f
ѵ = λ f



The velocity was 63.85 cm/s. The frequency was 2.69 Hertz. The period was 0.371 seconds. The velocity of the wave based on the wavelength and frequency was 63.27 cm/s. Thus the connection between is that the two results are effectively the same: the speed of the wave is the speed of the caster wheel board RipStik. 


The method of propulsion is known as sinusoidal propulsion. 

Comments

  1. Feiteira18 March, 2011 11:08

    you must be a great teacher!

    ReplyDelete
  2. Anonymous04 September, 2011 03:38

    Where did the expression "sinusoidal propulsion" come from? I can find no other instances of it. Did you coin it yourself?

    ReplyDelete
  3. Dana Lee Ling05 September, 2011 07:41

    No, I did not coin the phrase. I came across the term when reading through patents involving self-propelled skate boards such the balancing skateboard. A Google search of the term also turns up a number of other references. The concept is also related to propulsion on ice skates by swizzling.

    ReplyDelete

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