T: From the unit, we have learned that cars can't go without wheels, petrol and other parts. Would you like to draw a line of this procedure: the wheel - motor cars - other means of transportation?

Sa: How the wheel developed into a functional invention.

The wheel is everywhere on all our cars, trains, planes, machines, wagons, and most factory and farm equipment. What could we move without wheels? But as the wheel is an important invention, we don't know who exactly made the first wheel.

The oldest wheel found in archeological excavations was discovered in what was Mesopotamia and is believed to be over fifty-five hundred years old.

Development of a Functional Wheel

The following steps and developments took place to invent a functioning wheel, more or less in this order:

This is Heavy

Humans realized that heavy objects could be moved easier if something round, for example a fallen tree log, was placed under it and the object rolled over it.

The Sledge

Humans also realized a way to move heavy objects, with an invention archeologists call the sledge.

Logs or sticks were placed under an object and used to drag the heavy object, like a sled and a wedge put together.

Log Roller

Humans thought to use the round logs and a sledge together.

Humans used several logs or rollers in a row, dragging the sledge over one roller to the next.

Inventing a Primitive Axle

With time went on, the sledges started to wear grooves into the rollers and humans noticed that the grooved rollers actually worked better, carrying the object further. This was simple physics, if the grooves had a smaller circumference than the unworn parts of the roller, then dragging the sledge in the grooves required less energy to create a turning motion but created a greater distance covered when the larger part of