Wheel facts for kids
Spoked wheel of reconstructed Celtic funerary wagon, 550 BCE, Hochdorf Chieftain's Grave, Germany
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| Type | Invention |
|---|---|
| Inventor | First recorded use in Sumer (modern-day south-central Iraq) |
| Inception | Before c. 3500–3350 BCE |
| Manufacturer | Lua error in Module:WikidataIB at line 168: attempt to index field 'wikibase' (a nil value). |
| Available | Globally |
| Website | Lua error in Module:WikidataIB at line 168: attempt to index field 'wikibase' (a nil value). |
A wheel is a circular object that turns around an axle. It is one of the most important inventions in human history. Together with the axle, it forms the wheel and axle. This device is one of the six simple machines. Wheels make moving heavy loads much easier. They are used everywhere in modern transport. You can see wheels on cars, trains, bicycles, and airplanes. Wheels are also found inside machines. Examples include a ship's wheel, a steering wheel, a potter's wheel, and a giant flywheel.
A wheel helps things move smoothly by reducing friction. When an object rolls, it touches the ground with less rubbing force than sliding. To make a wheel spin, an outside force or torque must act on it. Gravity or human effort can provide this turning force.
Contents
How the Wheel Was Invented
Long before the wheel, people used heavy round tree logs as rollers. They placed logs underneath large stones to roll them along the ground. Later, people created solid wooden disks that could turn on an axle. The invention came after the invention of agriculture and the craft of pottery.
- 4500–3300 BCE (Copper Age): People invented the potter's wheel and created the earliest wooden carts.
- 3300–2200 BCE (Early Bronze Age): Wheeled carts spread across Europe and Asia.
- 2200–1550 BCE (Middle Bronze Age): Builders invented the spoked wheel and the swift chariot.
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The earliest clay disks for making pots appeared in the ancient Middle East. A very old wooden wheel was discovered in Slovenia. It is known as the Ljubljana Marshes Wheel. Scientists found that it dates back more than 5,000 years to the Copper Age.
Archaeologists found pictures of early wagons on ancient clay tablet pictographs in Mesopotamia. These carvings came from the city of Uruk, built by the Sumerian people. Similar ancient vehicles also appeared in Eastern Europe within the Cucuteni–Trypillia culture. An ancient container named the Bronocice pot shows one of the oldest pictures of a wagon. Workers discovered it during an excavation of a Funnelbeaker culture site in Poland.
The Invention of Spoked Wheels
Early wheels were heavy disks carved from tree trunks or planks of wood. These flat disks worked, but they moved slowly. During the Bronze Age, craftspeople created wheels with radiating wooden rods called spokes.
The Sintashta culture built some of the earliest spoked wheels around 2000 BCE near Krivoye Lake. These wheels were lighter and faster than solid wooden disks. People attached them to a two-wheeled chariot pulled by horses. The domestication of the horse allowed travelers to cover vast distances rapidly. Soon, ancient warriors in Greece, Egypt, and Mesopotamia used fast chariots. Celtic builders later added a tough iron band around their wooden wagon wheels.
Wheels Around the Ancient World
Ancient builders in China also created fantastic wheeled vehicles. Archaeologists discovered ancient wheel ruts at Pingliangtai from the Longshan Culture. Later evidence was found at Yanshi from the Erlitou culture. Early wooden wheel hubs also appeared in Qinghai.
In Britain, archaeologists found a preserved wooden wheel at the Must Farm site. It was carved around 1000 BCE and still had its central hub.
In Mesoamerica, people built small wheeled figures and toys. They did not build large wagons for transportation. This was partly because they lacked large work animals like cattle or horses. The native American bison was too wild to train. The llama lived in the Andes, but it was used as a pack animal. Indigenous cultures in Mesoamerica used a small spinning weight called a spindle whorl instead.
In Africa, people in Nubia used wheels to shape pottery and scoop water using a water wheel. Modern bicycles later gained wire-spoked wheels and air-filled pneumatic tires. Today, many cars use strong alloy wheel designs made from light metals.
How Wheels Work
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Dragging a heavy box along the ground takes an enormous amount of effort. The ground constantly drags against the bottom of the box. This resisting force is called friction.
When you put wheels on that box, moving it becomes much easier. The surfaces no longer rub against the rough dirt. Instead, smooth parts turn inside a clean hole called a bearing. A simple hole supporting an axle is called a plain bearing.
Calculating the Energy Saved
Scientists measure force in units called newtons and energy in joules. To find the work needed, multiply force by the distance moved.
Imagine pulling a heavy 100-kilogram stone across a dirt road for 10 meters. The rough ground creates a large resisting friction force. Dragging the stone uses nearly 5,000 joules of energy.
Now place the same heavy stone onto a cart with four wheels. The wheels roll forward smoothly across the road. The only sliding happens where the small axle turns inside its smooth hole. Because the axle has a small diameter, it slides only a tiny distance. The rolling cart requires around 123 joules of work. That means the wheels save more than 95 percent of your effort.
A rolling wheel loses only a tiny bit of power to rolling resistance. This small slowdown happens when rubber bends or dirt compresses under the wheel.
Parts of a Modern Wheel
A wheel might look simple, but it has several clever engineered parts. Each part has a special job that keeps vehicles rolling safely.
The Outer Rim
The rim is the circular outer edge of the wheel structure. It forms the round metal frame that holds the tire in place. On an ordinary bicycle wheel, the rim is the metal hoop connecting the spokes.
The Central Hub
The hub is the sturdy center part of any wheel. The rotating axle connects directly to the middle of the hub. Inside the hub, precision parts called bearings let the wheel spin freely. Some unusual vehicles use a special hubless wheel, where the center remains hollow.
Supporting Spokes
A spoke is a rod connecting the center hub to the outer rim. Ancient craftspeople shaved wooden rods using a special hand tool called a spokeshave. Modern bicycles use thin steel spokes under strong tension. These wire spokes make wheels extremely strong while remaining amazingly light.
The Protective Tire
A tire is the tough outer ring that wraps around the wheel rim. Early builders wrapped heated strips of iron around wooden cart wheels. When the metal cooled, it shrank tightly to bind the wooden pieces together.
Modern vehicles use inflatable rubber cushions called pneumatic tires. They are made from flexible natural rubber, durable synthetic rubber, and steel cables. The ridged surface on the outside of the tire is called the tread. Tread helps the vehicle grip the road, providing safe traction during rainy weather.
Special Attachments and Alternatives
Some vehicles must travel across soft sand, thick mud, or deep winter snow. Standard round wheels can sometimes get stuck in these harsh environments.
To prevent slipping on icy mountain roads, drivers wrap metal snow chains around tires. Deep snow tractors sometimes use wide treads called a continuous track to distribute weight.
In some places, people choose transport methods that do not use wheels:
- Fast maglev trains glide above metal guide tracks using powerful magnetic forces.
- Snow sleds, toboggans, and skis slide over deep winter snow without rolling parts.
- Watercraft like a hovercraft float along on top of thick cushions of air.
- Walking people and animals step over rocky boulders where circular wheels cannot roll.
Cultural Symbols of the Wheel
Because wheels turn in endless circles, many human cultures use them as symbols. A spinning wheel often represents the changing seasons and the passage of time. In ancient religions, artists drew the wheel of time to illustrate regular life cycles.
The famous dharmachakra appears on the modern national flag of India. This blue wheel symbol stands for truth, motion, and universal law. A red wheel also sits on the colorful flag of the Romani people. The wheel reminds us how human ingenuity can transform the entire world.
Images for kids
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A wheel with car tire made by BMW company
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Ezekiel's chariot vision by Matthaeus Merian
Related Pages
- Alloy wheel
- Axle
- Bicycle wheel
- Cogwheel
- Flywheel
- Potter's wheel
- Simple machine
- Steering wheel
- Tire
- Water wheel
- Wheel and axle
See also
In Spanish: Rueda para niños
