History

• It's impossible to pinpoint exactly when any of these simple machines was first used by humans, although there is ample evidence that they have been around for a very long time. It's obvious to anyone gazing at some of the wonders of the ancient world---the pyramids and Sphinx of ancient Egypt, for example---that these helpful tools played a key role in those mammoth construction projects.
  
  

Inclined Plane and Wedge

• A wheelchair ramp is an everyday example of a simple machine--an inclined plane
  
  The inclined plane, or ramp, is an adaptation from nature, mimicking a gently rolling hill. It is a refinement, of course, of the typical hill in nature, because its degree of elevation is uniform and its surface is smooth. It allows humans to move objects to a higher point without lifting them. It's far easier to roll a heavy object up a ramp than to lift it from the ground. The wedge, useful for splitting rocks, logs and other heavy objects, is two miniature inclined planes back to back, creating an object with a sharp pointed end that can be placed at the center of a log, for example, and struck on the blunt end to split the log.
  
  

Screw and Wedge

• Although it's a bit of a stretch, Philadelphia's Franklin Institute sees the screw as an adaptation of the inclined plane, describing it as an inclined plane that has been wrapped around a cylinder. "Every turn of a metal screw helps you move a piece of metal through a wooden space."
  
  

Lever

• The essence of simplicity, a lever is a stiff rod or bar that rests on a fulcrum or pivot point; pressure applied to the far end of the lever can raise or lift a weight at the other end. Examples of levers in everyday life include a crowbar, a hammer used to remove a nail from a piece of wood, and a bottle opener.
  
  

Wheel and Axle

• On its Inventor's Workshop website, Boston's Museum of Science describes this simple machine as "a wheel or spoke . . . locked to a central axle so that when one is turned the other must turn. A longer motion at the edge of the wheel is converted to a shorter more powerful motion at the axle. In reverse, a short powerful force at the axle will move the wheel's edge a greater distance."
  
  

Pulley

• In this variation of the wheel and axle, a cord wraps around the wheel, so that when the wheel rotates, the cord can move in either direction. If the cord is attached to a heavy object at a lower height, rotation of the wheel in a direction opposite to that of the attached object can lift it from its existing position.