### RipStik Sine Wave

In physical science unit nine I wanted to introduce the basic shape of a wave, the sine function, in a manner that was both eye-catching and comprehensible to a class of students who have not had any prior trigonometry. I placed a soaking wet cloth towel on the smooth cement floor. A meter beyond the wet cloth towel I placed a large sheet of presentation paper. I then rode a RipStik over the towel and swizzled on the paper. I had not practiced the maneuver nor did I know whether the paper would record the results in a satisfactory manner. I was quite pleased, however, when three runs produced at least on decent sine wave on the paper.
I then pinned the paper to the white board and used markers to delineate the sine wave. Even after the water dried, the swizzle mark sine wave remained as a faint line of dirt on the paper.

The demonstration also permitted me to introduce the concept of sinusoidal propulsion in a very concrete and observable way. The students have seen me move around the room, making sharp turns and navigating through tight squeezes between chairs. The students already know that the board is propelled by the swizzling action.

When I had first conceived of using a RipStik in physical science class my thoughts centered on using the RipStik to demonstrate gravitational potential energy and kinetic energy. Since then I have also used the RipStik in linear motion, accelerated motion, and now in sinusoidal motion.

Noting that the wheels undergo frictional heating when swizzling, one can almost imagine using a surface temperature thermal imaging device to determine the relationship between acceleration and thermal heating of the caster wheels for a given surface.

Optics, electricity, and cosmology may be beyond the reach of the stock RipStik, but there is a solid amount of physics that can be done with a caster board.