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Which is easier: lifting a piano ten feet up in the air or pushing it up a ramp until it is ten feet from the ground?
Most people would rather push the piano up the ramp.
Ramps, also called inclined planes, are simple machines. Simple machines are devices that make work easier. Levers, wheels, screws, wedges, and pulleys are also simple machines. Other machines are compound, or complex, machines. These combine more than one simple machine and include computers, cranes, and cars.
Simple machines are so common that you may not see how much you rely on them. But without them, you would find it hard, if not impossible, to get through a day.
◀ 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 that it is moved. Simple machines reduce the effort, or the push or pull, in work by increasing the distance. For example, suppose 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 is less effort. But you must apply the effort over a longer distance. In both cases, you are doing the same amount of work: less effort over a longer distance versus more effort over a shorter distance.
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▲ Heron of Alexandria (A.D. 100s) was nicknamed “machine man” because of his brilliant inventions. Heron was a Greek, and the first writer to group simple machines together. In his book Mechanica, he explained how putting together two or more simple machines makes a complex machine. A complex machine back then might have been a catapult or a ship’s sail.
Simple machines are grouped into two families. One is the lever family, and 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 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
