Grouping: Pairs
Take-home: Working wind-powered cart
Key ideas: Wind force, wheel/axle alignment, friction, sail area, vehicle design.
Start with: Use a fan to compare two carts with different wheel alignment or sail size.
Success check: Cart travels a set distance under fan power.
Try changing: Wheel type; sail shape/area; axle alignment; mass.
Preparation: Prepare axle holes/connectors; make one aligned example and one high-friction example.
Lesson flow: Day 1: Build chassis + axles + wheels → rolling test
Day 2: Add sail → fan trials → compare wheel/sail changes
Safety and cleanup: Teacher manages skewers/cutting/hot glue; fans stay behind marked line; retrieve carts only after fan stops.
