Grouping: Individual
Take-home: Rubber-band-powered car
Key ideas: Elastic energy, wheel/axle friction, alignment, gearing by axle diameter.
Start with: Wind a sample car and compare an aligned axle with a rubbing axle.
Success check: Car travels a minimum set distance under rubber-band power.
Try changing: Axle diameter; rubber-band wind count; wheel size; chassis mass.
Preparation: Make a reliable model and prepare axle/wheel sets.
Lesson flow: Day 1: Build → wind/release → alignment fixes → distance trials
Video:
How To Make a Mini Rubber Band Car
Safety and cleanup: Use controlled floor lanes; rubber bands remain attached to car; safety glasses if tension is high.
https://www.youtube.com/watch?v=VW_09myuISA