First thing in the morning, you walk down an inclined plane and use a pulley to let some light into the house.
You turn a screw to wash your hands. Then, you use a wedge to spread butter on your toast. Although you may not think of stairs, window blinds, faucets and knives as machines, they technically are.
You probably learned about simple machines at some point in elementary school — in other words, it’s probably time for a refresher. Here’s everything you need to know about simple machines explained in plain English.
Although the terms “work,” and “force,” are very similar, they actually have slightly different meanings in physics. When you move energy from one point to another, it’s known as work. How do you perform work? You do it by applying force, meaning pushing or pulling on something. The equation for this is:
Work = Force × Distance.
That means when you push or pull on an object and move it a certain distance, you’re performing work. Simple machines make work easier by reducing, multiplying or changing the direction of a force. For example, if you tried to carry a 100-kg box of bricks down the street, you probably wouldn’t get very far. Even pushing the box along the ground would be a monumental task.
But, add a wheel and axle — a type of simple machine — to the bottom of the box, and you get a wheelbarrow that enables you to haul loads many times heavier than your own body weight. The wheelbarrow also uses levers as handles that allow you to move the box upwards, applying most of the force to the wheel.
Two or more simple machines working in tandem is known as a complex machine. A bin lorry uses wheels and a lever for the drivers to control the vehicle’s rear loader. Although the UK aims to recycle 65% of its municipal waste by 2035, these heavy-lifting machines play a crucial role in taking rubbish to the dump in the meantime.
Other examples of complex machines you likely encounter in daily life include bicycles, can openers and lawn mowers.
Renaissance scientists placed simple machines into six categories based on their shape and how they reduce, multiply or change the direction of a force. Simple machines explained emerging concepts like the laws of friction.
This was probably the first simple machine because of how easy it is to create. The first time someone wedged a stick under the edge of a rock, pushed down on the other end of the stick and lifted the rock, they essentially invented the lever.
A lever is any long tool you put under an object to lift it. When you use a bottle opener to pop the lid off a can, you’re using this type of simple machine. A lever is even more effective when it has a fulcrum, which is an object placed under the middle of the lever to brace it.
A seesaw has a fulcrum in the middle both to raise the plank off the ground and allow you to lift the person on the other end. The closer the fulcrum is to the object you’re trying to lift, the easier it is to hoist the object in the air.
Think about it — if the fulcrum under the seesaw was right next to you, you’d have a much harder time lifting the person on the other end. You’d have to push down extremely hard on the board.
But if the fulcrum was close to your friend’s side of the board, just a small amount of force on your end would catapult them into the air! Your friend weighs the same in both cases, but the lever and fulcrum can work for or against you.
When you combine a wheel and axle with a rope to move objects up and down or back and forth, it’s known as a pulley. Pulleys change the direction of a force.
If you pull down on the rope of a flagpole, the flag goes up, not down. Imagine how hard it would be to push a flag up a flagpole! Ship sails, window blinds, elevators and cranes all use this type of simple machine to move objects and people.
Which is easier — scaling a vertical mountainside, or winding your way around the mountain in a spiral until you reach the top? In the first scenario, you’re technically travelling a shorter distance, but the effort is much harder. In the second situation, you’re walking a longer way, but it’s a much easier experience.
This is the difference between nails and screws. Pushing a nail straight into a piece of wood means the nail doesn’t have to travel far, but you have to apply a lot more force to it. Slowly winding a screw into a piece of wood means it travels a longer distance, but you don’t have to apply as much force. The screw’s threads give it a mechanical advantage when you rotate it.
Also called a ramp, an inclined plane is a diagonal surface — in other words, one end is higher than the other. The difference between an inclined plane and a lever is that the inclined plane’s surface doesn’t move up and down.
Ramps allow you to easily move a heavy object up or down by pushing on it horizontally. Ramps, levers and perhaps other simple machines explain how the Egyptians built the pyramids.
A wedge is basically an inclined plane, but you use it to separate objects or fasten them together rather than moving things along its surface. It converts the force you apply to the blunt end into a force perpendicular to its inclined surfaces. An axe, saw, needle, staple and nail are all examples of wedges.
Invented around 6,000 years ago, the wheel is one of humankind’s most significant innovations. But, it wouldn’t be possible without the axle, which is the horizontal bar going through the wheel’s center. The axle serves as an attachment point between the wheel and the vehicle. It also allows the wheel to spin without flying off.
Wheels can increase speed or force, but not both at the same time. When you turn the wheel’s rim, the axle turns more slowly but with more force, so the wheel becomes a force multiplier. When you turn the axle — which is what a car does — the wheel multiplies speed instead. The axle doesn’t turn for a very great distance, but it leverages the wheel to turn the outer rim much farther, increasing the vehicle’s speed.
Whether you realize it or not, you use simple machines every day. Modern life would be impossible without them. Between wheels and axles, pulleys, inclined planes, screws and levers, you’ll find the basic components of every complex machine on the planet. That’s simple machines explained in a nutshell.