the log roller turned.

The log roller was becoming a wheel, humans cut away the wood between the two inner grooves to create what is called an axle.

First Carts

Wooden pegs were used to fix the sledge, so that when it rested on the rollers it did not move, but allowed the axle to turn in-between the pegs, the axle and wheels now created all the movement. These were the first carts.

Improvements to the cart were made. The pegs were replaced with holes carved into the cart frame, the axle was placed through the hole. This made it necessary for the larger wheels and thinner axle to be separate pieces. The wheels were attached to both sides of the axle.

Fixed Axles Make a Functional & Successful Wheel

Next, the fixed axle was invented, where the axle does not turn but is solidly connected to the cart frame. Only the wheels did the revolving by being fitted onto the axle in a way that allowed the wheels to rotate. Fixed axles made for stable carts that could turn corners better. By this time the wheel can be considered a complete invention

Activity two: Stimulate students' curiosity

T: Since Henry Ford's motor car came into being, American cars have been the rule of cars all over the world until in the 1960s. Meanwhile a lot of stylish but cheaper cars were coming out of Europe, American-made cars stopped being as popular. If you were a car designer, what kind of car would you like to create?

Let students discuss in pairs and they may also do some drawings.

Step Ⅱ Guidance on scientific procedures

Activity one: Look at the examples

T: Now please turn to page 47. Look at the Bulletin Board on this page and find what the topic of this Bulletin Board is about.

Ss: The Bulletin Board is about the Car Museum.

T: In what way does the host of the bulletin want to present its works?

Ss: It wants to hold a special Car Design Exhibition.