Lesson 04 – What Is a Gear?

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Read About Gears


Read the vocabulary terms to understand the reading better.

A gear is a wheel that has teeth around its edge. The teeth of one gear fit into the spaces between the teeth on the other gear.

In a gear train, several gears contact each other. Each gear moves in the opposite direction of its neighbours.

What Is a Gear?

A gear is a wheel that has teeth around its edge.
The teeth of one gear fit into the spaces between the teeth on the other gear.

When one gear turns, it makes the other gear turn. The second gear wheel will turn in the opposite direction to the first gear. See if you can picture this in your mind as you look at the diagrams.

When you connect several gears in a row, you are creating a gear train. When a force makes any one gear turn, all the gears in the gear train will turn. Each gear turns in the opposite direction to the gears beside it.

Gears and Speed

When we talk about speed, we are talking about how far something moves in a set period of time. Gears can be used to change the speed of movement. When one gear is connected to a gear of a different size, the two gear wheels will move at different speeds.

Look at the two gear wheels shown. When the large gear wheel moves, it makes the smaller gear move. The smaller gear will move faster than the larger gear. Why does this happen?

One tooth on the large gear will move one tooth on the small gear. When the large gear makes one half of a turn, the small gear will make a full turn. The small gear moves twice as fast as the large gear because it has half as many teeth.

By using gears that are two different sizes, we can change the speed of the motion.

To learn more about gears, watch the videos by Childrens Museum Houston and NG Science on Youtube.

Complete the candy gear activity below to learn more about gears!

Now Show What You Know!

Complete some questions about the reading selection by clicking “Begin Questions” below.