Book 3, Question 14
Why Do Bikes Have Gears?
Gears change how far the bike goes for each turn of the pedals. A low gear is small steps, and a high gear is long steps. Low gears help on hills, and high gears help with speed!
From the book
Page from A Million Whys Book 3
More fun facts
- A gear is a wheel with teeth around its outside edge.
- Gears, like levers and pulleys, can let a small effort move a bigger load.
- By counting the teeth on two linked gears, you can work out the gear ratio, or how many times one turns for each turn of the other.
- In a BBC experiment, riders on 18 bikes set in very low gears pulled a piano uphill.
- The earliest gears can probably be traced back to the fourth century B.C.
- The first bike-like machine, the draisine, had no pedals at all. Riders pushed their feet against the ground.
Sources: BBC, BBC, NASA, National Geographic Kids
Questions kids ask
What is a gear ratio?
It compares the teeth on two linked gears. It tells you how many times one gear turns for each turn of the other.