A gear is a wheel with teeth along the outer edge. By itself a gear cannot do much of anything. But in combination with other gears a lot of things can happen. Gears can transfer effort from one place to another. There are gears inside almost every machine, that connect the roatating parts.
Gears can change the direction of the rotating parts and can change the form of mechanical motion.
The best way to find out how gears work is to make some of your own to experiment with. For this lesson students will be making gears from corrugated cardboard and plastic lids. The corrugations face out to make gear teeth. Students will make a gear system and observe how the gears interact. Lesson is extended so students can use their gears in a planetary system, similar to a spirograph.