A World of Wedges
Where else besides the kitchen can you find wedges? Let’s go on a “wedges hunt” and find out. You won’t have to look far.
Just check out almost any garage or toolbox. Nails are wedges. So are thumbtacks and pushpins. They are like the tines of a fork. After these wedges are driven into a material, such as wood or cork, friction holds them in place. That’s how a wooden chair stays together. And that’s how your latest and greatest science report stays pinned to the bulletin board.
Lots of garden equipment is made of wedges. These include the blades of shovels, hoes, and weeding tools—pretty much anything designed to dig. Wedges are great for cutting, too, like the blades of lawn mowers and garden shears.
Want to think bigger? How about the blade of a bulldozer and the plows on farm equipment? Snowplows use wedges to scrape snow off roads. The shape of the wedge allows the plow to reach beneath the snow and lift off the road.
When you pull down on a zipper tab, a small wedge inside the slider pushes the teeth apart.
Some wedges are easy to see, and you can tell right away how they work. For instance, you can see how a sculptor uses a chisel to break off bits of rock while creating a statue. But some tools have wedges hidden inside them. You can’t see the wedges, yet the tool couldn’t work without them. One of these tools is something you probably use every day. It’s on pants, jackets, book bags, and lots of other things. Can you guess what it is? It’s a zipper!
You wouldn’t be able to apply enough force with only your fingers to interlock the two sides of a zipper. But it’s easy with wedges. When you pull up on the zipper, small wedges inside the slider push the teeth together. When you pull down, another wedge separates the teeth, like a tiny axe splitting wood.
Wedges on the Move
So far, most of the wedges you have read about cut through solid matter, like wood, soil, and food. But liquids and gases are matter, too. Do wedges cut through this matter? Sure, just look at the front of a boat. The wedge shape of the bow lets the boat slice through the water with ease.
Designers of all kinds of vehicles take advantage of wedges. Have you ever noticed how the front of cars, planes, and trains usually are narrower than the rest of the vehicle? That general wedge shape makes it easier for the vehicle to push away all of the air particles as it moves. Then it can go faster, use less effort, and therefore use less fuel.
Shaping vehicles like wedges is a great idea, but all we’re doing is following nature’s lead. Many animals have a sleek wedge shape that helps them move swiftly. Bird beaks are a great example. So are the sleek shapes of dolphins and most sharks. Their tapered body helps give them the speed with less effort.
Back at the Campsite
Now that you know something about wedges, think about some ways you might use this simple machine on a camping trip.
Here’s a question to jumpstart your thinking: What would you use to roast marshmallows over that campfire you helped start?