The Simple Machines

A simple machine is a mechanical device that changes the direction or magnitude of a force.[2] In general, they can be defined as the simplest mechanisms that provide mechanical advantage (alsocalled leverage).[3]
Usually the term refers to the six classical simple machines which were defined by Renaissance scientists:[4]
* Lever
* Wheel and axle
* Pulley
* Inclined plane
*Wedge
* Screw
A simple machine is an elementary device that has a specific movement (often called a mechanism), which can be combined with other devices and movements to form a machine. Thussimple machines are considered to be the "building blocks" of more complicated machines. This analytical view of machines as decomposable into simple machines first arose in the Renaissance as aneoclassical amplification of ancient Greek texts on technology,[5] and is still a central part of engineering in today's age of applied science. For example, wheels, levers, and pulleys are all used in themechanism of a bicycle.[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 simplemachines 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 broader sense is 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 (suchas "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 Ephraim Chambers[1] (in the figure...