Designing cars propelled by balloons was a fun challenge for everyone. Students defined and measured their cars performance in terms of distance and speed. Variables tested were balloon size, tire type, and car weight. Problems encountered and resolved included:
Using three wheels in order to reduce friction
Building plates or platforms on the cars to keep the balloons away from the tires
Streamlining the car shape in order to reduce drag
Associating the "neck" of the balloon to an exhaust pipe on a real car in order to solve the problem of how to attach the balloon to the lego car
Using weight to balance and help it go straight
This was a popular challenge which interested the students immediately. We used three hour blocks for designing and a final class for sharing of data and a derby race.