Wheels and axles make moving easier — Physical education, 7–10 years
A wheel turns around an axle, allowing an object to roll instead of scraping along the ground. This can make moving loads easier, but it does not remove all effort.
Idea
A wheel is a round object that turns around an axle. When the wheel rolls, only a small part touches the ground at each moment, so the object moves without scraping its whole bottom along the surface. The axle keeps the wheel in place while it turns.
Why
Before wheels were used, people had to drag heavy loads, making the whole underside rub against the ground. Rolling changes that kind of rubbing into turning, which usually needs less force on a firm surface. Wheels solved the problem of moving loads over land more easily and repeatedly.
Worked example
A toy cart has four wheels. Push it 3 metres across the floor and watch the wheels turn as the cart moves forward. Now place the same cart on its side and drag its flat base 3 metres. The cart still travels 3 metres, but its base scrapes along instead of rolling.
Common trap
It is tempting to think wheels make any load easy to move. That is reasonable because a wheeled suitcase feels much easier than a suitcase we drag. But a flat tyre, a rough surface, a heavy load or a jammed axle can still need a lot of force; wheels reduce some resistance, not every resistance.
In the world
Shopping trolleys, bicycles, wheelbarrows and suitcases use wheels and axles to move people or loads. A bicycle’s wheels roll while the axles hold them to the frame, and turning the axle through the pedals helps the bike travel. Different wheels suit different surfaces and jobs.
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