Which is easier? Lifting a piano ten feet up in the air? Or pushing it up a ramp until it’s ten feet from the ground?
Most people would say pushing it up a ramp.
Ramps are also called inclined planes. They are one type of simple machine. Simple machines make work easier. Levers, wheels, screws, wedges, and pulleys are other kinds of simple machines. Then there are compound, or complex, machines. These combine more than one simple machine. Some examples are computers, cranes, and cars.
Simple machines are so common, you may not see how much you need them. But without them, you’d find it hard to get through a day. It might even be impossible!

◀ Simple machines help people do work. To scientists, work is not the opposite of play. Work is the effort, or force, needed to move an object times the distance it is moved. Simple machines reduce the effort, or the push or pull, in work. They do that by increasing the distance. For example, what if you have to put a 50-pound box of books into the back of a truck that is five feet off the ground? You could lift the box straight up into the truck. Or you could push it up a ramp. Pushing it up the ramp takes less effort. But you have to use the effort over a longer distance. You do the same amount of work either way. It’s just that one way uses less effort over more distance. And the other uses more effort over less distance.
▲ Heron of Alexandria (A.D. 100s) was nicknamed “machine man.” That’s because he made brilliant inventions. Heron was a Greek. He was the first writer to put simple machines together. His book Mechanica explained how connecting two or more of them makes a complex machine. A complex machine back then might have been a catapult or a ship’s sail.
Simple machines are put into two families. One is the lever family. The other is the inclined plane family. That’s because both the wheel and axle and the pulley work on the same principles as the lever. And the wedge and screw are inclined planes in disguise. ▼

Lever Family

Lever
Date invented: prehistoric
First known use: probably by earliest humans to dig for small animals or to pry under rocks
Examples: bottle opener, fishing rod, nutcracker

Wheel and Axle
Date invented: around 4000 to 3500 B.C. in the Middle East
First known use: potter’s wheel
Examples: tires, spinning wheel, windmill

Pulley
Date invented: around 8000–1000 B.C.
First known use: probably as part of a crane
Examples: flagpole, clothesline, elevator
Inclined Plane Family

Inclined Plane
Date invented: prehistoric
First known use: raising structures, such as the pyramids in the Middle East and Egypt, though surely used before
Examples: ramp, mountain road, escalator

Screw
Date invented: 400s to 200s B.C.
First known use: hand-cranked water pumps in Egypt and the Middle East
Examples: drill, propeller, corkscrew

Wedge
Date invented: prehistoric (archaeologists date it to around 2.6 million B.C.)
First known use: as stone tools for hunting and building
Examples: chisel, axe, arrowhead
A car is a very complex machine. It is made up of many simple machines. ▼

Trunk Lid
Lever
Tire
Wheel and Axle
Nuts
Screw
Seats
Inclined Plane
Door
Lever
Stick Shift
Lever
Steering Wheel
Wheel and Axle
Wheel
Wheel and Axle
Hood
Lever
Fan Belt
Pulley
Car Body
Wedge