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Forces and Motion - RAFT Retractor Car

As part of the forces and motion unit my students had the opportunity to play around with the RAFT Retractor Car Activity Kit. The modified activity [available at] involved the students building the vehicle [as specified by the project page] then deciding what they wanted to test. Students had several options:
  • how will the car perform over various surface types?
  • how might the speed or distance be impacted if the car has to travel up an incline?
  • how would increasing the mass on the car impact the speed or distance the car travels?
  • how could the design be adjusted to make the car go further or faster?
As usual, only one person selected to try this activity, at least until the rest of the students saw the car cruise across the classroom floor. Thank goodness for those students who are ‘early adopters’ and willing to try something unknown. In the end there were several groups who performed the surface test; one group tried the incline, and two messed around with the design of the car.

The incline test was based on a using textbooks to create the rise. Students used a ramp propped on one, two, or three textbooks. We were collectively disappointed when the vehicle did not manage any of the inclines; however that did spark discussion about traction which lead to wondering if wider wheels would help or if the car needed more power [two retractors?].

The students who tried different surface areas [classroom tile, rough asphalt, and cement] had some interesting explaining to do in their lab report’s data analysis section. The car performed so well in the classroom it would consistently run out of room before it ran out of power! The students who were strictly testing distance would get false data because the car would go further on the cement just by the fact it was longer. We decided, at some other point, we would need to test the vehicle in the cafeteria which is twice the length of our classroom.

The re-designer teams tried two different modifications. The first team felt sturdier wheels would improve the vehicles performance. They upgraded the plastic lid wheels for the higher end compact disc option. Apparently flash is not everything. The vehicle did not perform better! The students were surprised and concluded the CDs may have been too thin to get enough traction on the floor. The second team wanted a car with more power so they upgraded their vehicle to the dual engine [two retractors] model. When it came down to the classroom version of “fast & furious” the twin engine car had faster pick up but ultimately did not go any further. Sad news for the betting crowd in the stands.

This learning would never come from a textbook. Thank you RAFT for providing inexpensive ways for students to explore science concepts in a real world application. There was dialogue, thinking, exploring, testing, hypothesizing, analyzing, failure, success, and fun. It does not get any better than this!

Cynthia Lipsig, Teacher and RAFT Fellow


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