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What is a wedge? This stone hand-ax from Chennai, India is a kind of wedge.

What is a wedge? This stone hand-ax from Chennai, India is a kind of wedge.

A wedge is a kind of inclined plane

What is a wedge? Like screws, wedges are really a kind of inclined plane, but they are so useful that people give them their own category among the simple machines. A wedge is two inclined planes back to back against each other.

What’s an inclined plane?
What’s a screw?
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When were wedges invented?

Wedges evolved on their own long before people. Sharp teeth are a kind of wedge that cuts through meat and vegetables when fish or crocodiles eat something.

More about teeth
When did fish evolve?

People have been using wedges in Africa since the earliest Stone Age, about 2.6 million years ago. These early wedges were stone hand-axes, and their sharp edges let people cut a hunk of meat off a gazelle to eat, or cut branches for firewood. Probably people also used wooden wedges to split bigger pieces of wood into smaller pieces.

Early stone tools
Primates and early humans

Wedges and mechanical advantage

What is a wedge? wooden wedges to split a log

Wooden wedges to split a log

The mechanical advantage you get from a wedge depends on how thick it is. A thick short wedge will split things apart faster, but you’ll have to push down on it with more force – maybe hit it with a hammer. A thin long wedge will be easier to drive in, but it will take longer to split something.

Hammers and levers

Some examples of wedges

Today we have many different uses for wedges. A plow is a kind of wedge. A knife is a kind of wedge, and a fork is made of four little wedges.

What is a plow?
Forks, nails, and cheap steel

Razors and scissors are wedges too. So are doorstops. A nail is a kind of wedge, and so is the pointed nose of an airplane, that helps it cut through the air more efficiently.

So what is a wedge? Did you find out what you wanted to know about simple machines? Let us know in the comments!

Learn by doing – wedges
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