Lesson 5: Moving Things: Wheels and Gears
Wheels changed human civilization. Gears multiplied that power into machines that can lift, grind, and move enormous loads with little effort. Let's explore rotational engineering.
Key Concepts
Why Wheels Work
A wheel reduces friction by rolling instead of sliding. Sliding a heavy box across the floor is hard. Put it on wheels and it rolls easily. Less friction means less force needed.
Gears
Gears are wheels with teeth. When two gears mesh, they transfer rotation. A small gear driving a big gear slows down the rotation but increases the turning force (torque). A big gear driving a small gear speeds things up but reduces force.
Gear Ratios
If a 10-tooth gear drives a 30-tooth gear, the output turns 3× slower but with 3× more torque. This ratio (30/10 = 3) is the gear ratio. Bicycles use gear ratios — lower gears for hills, higher gears for speed.
🆕 Gear Simulator
Click Run to see the gears turn. Change the gear sizes to see how ratio affects speed!
✅ Check Your Understanding
1. Why do wheels reduce friction?
2. What happens when a small gear drives a big gear?
3. A 10-tooth gear drives a 40-tooth gear. What is the gear ratio?