RipStik gravitational potential and kinetic energy

I opted to begin 041 as I did last summer and spring in physical science, using the RipStik to attempt to illustrate the trading-off of gravitational potential energy due to position for kinetic energy. The parking lot has a very gentle slope, downhill is free. Yes, I am lecturing while riding a RipStik. Loioshi-Anne was on the camera this session.

I started as I have the past two terms, with the RipStik up against a parking lot bumper. This is the position of zero potential energy, the bottom of the slope. Being an active parking lot, there are always cars. There will come a term when there is no empty parking slot for me to use. 

 

I mount the board and no motion occurs. I suppose that a U-shaped swale would work better, but at present no lot at the college has such a shape. The new Bank of Guam and shopping complex may yet include the necessary surface, but that would entail a field trip just for a demonstration. 

 

There is a slight depression between the administration building and the north "F" faculty building, maybe I should use that, but then I need to leave more time after the return and coverage of test one. I ran out of time this term.

I then move to the top of the parking lot and mount the RipStik without pushing off. Gravitational potential energy does all of the work for me, literally in the physics sense of work. I gain kinetic energy. I then use the unique properties of the RipStik to make a 180 degree turn and convert my kinetic energy back into gravitational potential energy.

I rolled uphill without swizzling the board, and then repeated the demonstration. Note that I have the undivided attention of the class.

This term I then showed the class that the board itself can be made to rise and fall slightly due to the angle of the castors.

The vertical motion of the board is small but significant - this is the energy pump that provides the ability to convert gravitational potential energy to kinetic that drives the board forward while swizzling. There is more to the system than the energy exchange - the whole system is very complex involving sinusoidal motion, side forces exerted by angles castors, and force vectors galore. From an energy perspective, however, the falling of the board is converted to kinetic energy.

In the above photo I have swizzled up the slope back to my starting location. Moving up hill requires swizzling which pumps the board up and down, in physics words, work must be done to gain gravitational potential energy. That work is being provided by my swizzling which drives the board vertically.

The next class session continues the exploration of gravitational potential and kinetic energy with a banana leaf marble ramp.

The class watching my demonstration. As an indirect assessment of attention being paid, the more typical reaction to a camera for my students is to flash Shaka hand gestures and pose. That the presence of the camera did not have this impact is a measure of the attention being paid. 

 

Bearing in mind that this activity is a pre-activity, a concept organizing activity, and that the concepts involved are both subtle and highly abstract, I do not expect any deep understanding of gravitational potential and kinetic energy at this point. If, however, I have garnered their interest, their attention, caused a spark of curiosity, then I have succeeded. On that spark I can build a larger flame of understanding.