Bicycles are easy to understand. The modern ones have only about 1,500 parts!
In the last century or so, bikes have been given some important upgrades. Two big ones are gears and hand-operated brakes. But the basic design hasn’t changed since the 1880s. Every bike has a foot-powered cog-and-chain system. Another word for rear cog is “sprocket.” The system sends energy from the pedals to the back wheel. This makes bicycles the most efficient form of human-powered transportation. It’s more efficient than walking, running, or riding scooters and skateboards.
