Lyceum A - Physics - Week 20 - Introduction to Gears

Gears are wheels with short spokes (called teeth) that slot together so that when one wheel (gear) is turned, the other gear turns as well.

From dkfindout.com:

If the gears are of different sizes, they can be used to increase the power of a turning force. The smaller wheel turns more quickly but with less force. Cars and bicycles use gears to achieve amazing speeds our bodies could never match without help.

Gears on a bicycle are usually connected by chain, but they work the same way as gears that are touching. The chain transfers the turning force from the pedals to make the wheels go around and move the bike along. The chain can be moved between gears of different sizes, either to increase the speed (for racing) or to increase the force (for climbing steep hills)

Gear Basics - onlinescience - 10:58min

https://www.youtube.com/watch?v=odpsm3ybPsA