Bicycle

Human-powered, pedal-driven, single-track vehicle
Two wheels attached to a frame, one behind the other
- bike (bicyclist)
- pushbike (biker)
- cycle (cyclist)
Forward motion dynamically balances and controls vehicle with steering inputs
- Not stable unless moving forward

Components of cycles
- chain-driven sprockets [chain-drive (1885)]
- ball bearings
- pneumatic tires
- spoke-tensioned wheels
- modern materials
- computer-aided design (specialized designs)