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Simple machineFrom Wikipedia, the free encyclopedia

This article is about the concept in physics. For theInternet forumsoftware, seeSimple Machines Forum.

Table of simple mechanisms, fromChambers' Cyclopedia,1728.[1]Simple machines provide a "vocabulary" for understanding more complex

machines.

A simple machineis a non-motorized device that changes the direction or magnitude of aforce.[2]

In general, a simple machine

can be defined as one of the simplest mechanisms that providemechanical advantage(also calledleverage).[3]

Usually the term refers to the six classical simple machines which were defined byRenaissancescientists:[4]

1. Lever

2. Wheel and axle

3. Pulley

4. Inclined plane

5. Wedge

6. Screw

A simple machine is an elementary device that has a specific movement (often called amechanism), which can be combined

with other devices and movements to form amachine.Thus simple machines are considered to be the "building blocks" of more

complicatedmachines.This analytical view ofmachinesas decomposable into simple machines first arose in the Renaissance

as aneoclassicalamplification ofancient Greektexts on technology,[5]

and is still a central part ofengineeringin today's age

ofapplied science.For example, wheels, levers, and pulleys are all used in the mechanism of abicycle.[6][7]Between the simple

machines and complex assemblies, several intermediate classes can be defined, which may be termed "compound

machines"[8][3][9]or "machine elements".[10]The mechanical advantage of a compound machine is simply the product of the

mechanical advantages of the simple machines of which it is composed.

Various authors have compiled lists of simple machines and machine elements, sometimes lumping them together under a

single term such as "simple machines",[1]

"basic machines",[6]

"compound machines",[8]

or "machine elements"; the use of the

term "simple machines" in this broadersenseis a departure from the neoclassical sense of the six essential simple machines,

which is why many authors prefer to avoid its use, preferring the other terms (such as "machine element"). In all cases, the

theme of an analytical and synthetic connection from simple to compound to complex is at work. A page from a 1728 text by

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Ephraim Chambers[1]

(in the figure to the right) shows more machine elements. By the late 1800s,Franz Reuleaux[11]

identified

hundreds of machine elements (calling them "simple machines"). Models of these devices can be found atCornell University's

KMODDL website.[12]

History

The idea of a "simple machine" originated with the Greek philosopherArchimedesaround the 3rd century BC, who studied the

"Archimedean" simple machines: lever, pulley, andscrew.[3][13]He discovered the principle ofmechanical advantagein the

lever.[14]

Later Greek philosophers defined the classic five simple machines (excluding theinclined plane)and were able to

roughly calculate their mechanical advantage.[5]

Heron of Alexandria(ca. 1075 AD) in his work Mechanicslists five

mechanisms that can "set a load in motion"; lever, windlass, pulley, wedge, and screw,[13]and describes their fabrication and

uses.[15]

However the Greeks' understanding was limited to thestaticsof simple machines; the balance of forces, and did not

includedynamics;the tradeoff between force and distance, or the concept ofwork.

During theRenaissancethe dynamics of the Mechanical Powers, as the simple machines were called, began to be studied from

the standpoint of how much useful work they could perform, leading eventually to the new concept of mechanicalwork.In 1586

Flemish engineerSimon Stevinderived the mechanical advantage of the inclined plane, and it was included with the other

simple machines. The complete dynamic theory of simple machines was worked out by Italian scientist Galileo Galileiin 1600

in Le Meccaniche("On Mechanics").[16][17]

He was the first to understand that simple machines do not createenergy,only

transform it.[16]

The classic rules of slidingfrictionin machines were discovered byLeonardo da Vinci(14521519), but remained unpublished in

his notebooks. They were rediscovered byGuillaume Amontons(1699) and were further developed byCharles-Augustin de

Coulomb(1785).[18]

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A machine is a tool used to make work easier. Simple machines are simple tools used to make work easier.Compound machines have two or more simple machines working together to make work easier.

In science, work is defined as a force acting on an object to move it across a distance. Pushing, pulling, and

lifting are common forms of work. Furniture movers do work when they move boxes. Gardeners do workwhen they pull weeds. Children do work when they go up and down on a see-saw. Machines make their work

easier. The furniture movers use a ramp to slide boxes into a truck. The gardeners use a hand shovel to helpbreak through the weeds. The children use a see-saw to go up and down. The ramp, the shovel, and the see-

saw are simple machines.

Inclined PlaneA plane is a flat surface. For example, a smooth board is a plane. Now, if the plane is lying

flat on the ground, it isn't likely to help you do work. However, when that plane is inclined,

or slanted, it can help you move objects across distances. And, that's work! A commoninclined plane is a ramp. Lifting a heavy box onto a loading dock is much easier if you slide

the box up a ramp--a simple machine. Want to know more? Here'sextra information.

WedgeInstead of using the smooth side of the inclined plane, you can also use the pointed edges todo other kinds of work. For example, you can use the edge to push things apart. Then, the

http://weirdrichard.com/inclined.htmhttp://weirdrichard.com/inclined.htmhttp://weirdrichard.com/inclined.htmhttp://weirdrichard.com/inclined.htm

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inclined plane is a wedge. So, a wedge is actually a kind of inclined plane. An axeblade is a

wedge. Think of the edge of the blade. It's the edge of a smooth slanted surface. That's a

wedge! Want to know more? Here'sextra information.

ScrewNow, take an inclined plane and wrap it around a cylinder. Its sharp edge becomes another

simple tool: the screw. Put a metal screw beside a ramp and it's kind of hard to see thesimilarities, but the screw is actually just another kind of inclined plane.Try this

demonstrationto help you visualize. How does the screw help you do work? Every turn of ametal screw helps you move a piece of metal through a wooden space. And, that's how webuild things! Want to know more? Here'sextra information

LeverTry pulling a really stubborn weed out of the ground. You know, a deep, persistent weedthat seems to have taken over your flowerbed. Using just your bare hands, it might be

difficult or even painful. With a tool, like a hand shovel, however, you should win the battle.

Any tool that pries something loose is a lever. A lever is an arm that "pivots" (or turns)

against a "fulcrum" (or point). Think of the claw end of a hammer that you use to pry nailsloose. It's a lever. It's a curved arm that rests against a point on a surface. As you rotate the

curved arm, it pries the nail loose from the surface. And that's hard work!

Wheel and AxleThe rotation of the lever against a point pries objects loose. That rotation motion can also do

other kinds of work. Another kind of lever, the wheel and axle, moves objects across

distances. The wheel, the round end, turns the axle, the cylindrical post, causing movement.On a wagon, for example, the bucket rests on top of the axle. As the wheel rotates the axle,

the wagon moves. Now, place your pet dog in the bucket, and you can easily move him

around the yard. On a truck, for example, the cargo hold rests on top of several axles. As thewheels rotate the axles, the truck moves.

PulleyInstead of an axle, the wheel could also rotate a rope or cord. This variation of the wheeland axle is the pulley. In a pulley, a cord wraps around a wheel. As the wheel rotates, the

cord moves in either direction. Now, attach a hook to the cord, and you can use the wheel's

rotation to raise and lower objects. On a flagpole, for example, a rope is attached to a pulley.

On the rope, there are usually two hooks. The cord rotates around the pulley and lowers thehooks where you can attach the flag. Then, rotate the cord and the flag raises high on the

pole.

If two or more simple machines work together as one, they form a compound machine. Most of the machines

we use today are compound machines, created by combining several simple machines. Can you think of

creative ways to combine simple machines to make work easier? Think about it.

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