Wheel

Think about all the things that use wheels. Cars and trucks have wheels. Rollerblades have wheels. Bicycles have wheels. Shopping carts and suitcases have wheels. The wheel is one of the most important inventions in history.

WHAT ARE WHEELS?

Wheels are round. Wheels can be solid disks. Or they can be round hoops with spokes to make them stronger, like bicycle wheels.

Without wheels we would have to drag everything around over the ground. Moving things with wheels is a lot easier.

Wheels are often used in pairs. A rod connects two wheels. The rod is called an axle. Some axles turn with the wheels. Other axles do not turn. The wheels turn around the axle. Wagons and cars have axles.

THE INVENTION OF THE WHEEL

The wheel was invented more than 5,000 years ago. The simplest wheels were solid wood disks. Wooden pins held these wheels to an axle.

Wheels were first made in an ancient country in the Middle East called Mesopotamia. People put wheels on carts. Wheels let animals pull carts with heavy loads.

Today, motors make axles and wheels turn around. Wheels let cars go fast for long distances. Wheels let trucks and trains pull very heavy loads.