Lever – The lever is a rigid object -a bar, for example- that is set upon a pivot point or fulcrum. When force is applied to one end, that force is magnified by the fulcrum, allowing for very heavy objects on the other end of the bar to be lifted.
Wheel and Axle – When the circular wheel is attached to the end of an axle (a rigid pole), any force that makes the wheel turn also makes the axle spin. This actually magnifies that force. Alternatively, force can be applied to the axle to make the wheels rotate.
Pulley - The pulley is a mounted wheel that has a groove cut into its circumference. One end of a rope or cable is threaded into this groove with the other end attached to an object to be lifted. When force is exerted on the opposite end of the rope, that force is re-directed and amplified by the pulley wheel, incorporating your own weight into the force exerted in lifting. This reduces the amount of force needed to lift or move that object. The more pulleys incorporated, the less force required to lift the object.
Inclined Plane – The inclined plane is simply a flat surface that is placed at an angle to any other surface. Less force is required to move something up the inclined plane than would be required to lift something straight up the same height distance. The lesser the incline, the less force required to move the object (however, distance is increased). A steeper, shorter incline will require more force than a longer, less-steep incline.
Wedge – A wedge is a double-inclined plain, which means that both of its sides are inclined. When the point of the wedge is pushed between two objects, it takes the force behind it and exerts it along the two sides, moving the objects apart.
Screw – A screw is a shaft that has a small inclined grove cut into its surface. When the screw is turned, the rotational force applied to the groove is translated into a linear force, making it easier to insert the screw into the object or material being worked with.
The 6 Simple Machines – a list of these machines with more information on how they work
How the 6 Simple Machines Work – a bit more explanation
Simple Machines – the Wiki for these six machines
Let's take a closer look at how several of these simple machine principals are applied in modern machinery.
The Lever – Several examples of a lever include the crowbar and the seesaw, but these are very basic examples. Anything that is used to lift something up can be seen as a lever. For example, a forklift uses the principle of the lever to lift heavy loads. A large amount of counter weight is built into the rear of the forklift. The front wheels function as the fulcrum (or pivot pint) and pneumatics aid in the exertion of force on forklift tines that function as the lever.
The Wheel and Axle – The main use of the wheel and axle is very easy to identify: the tires on any vehicle make use of wheels and axles. Cars, airplanes, construction equipment… anything with tires makes excellent use of this simple machine.
The Pulley and counter-weighting – Cranes use a counterweight in order to make certain the crane doesn’t tip over (they are often mounted to a concrete or steel base as well) and a multiple-pulley system to reduce the amount of force needed to lift a heavy load.
An Illustrated Guide to the Six Simple Machines – also discusses their uses today
Simple Machines in Everyday Life – how some simple machines are used today
Simple Machines Found in Your Home – we see simple machines every day at home
How Simple Machines Make Work Easier – examples of how we use these machines
One great example of a modern machine that incorporates several simple machines into one is the forklift. This piece of equipment is essentially a large, technologically-advanced lever, with the front tires actually functioning as the “fulcrum” in this simple (but complex) machine. A forklift’s wheelbase and track (which make use of the wheel and axle), and its counterweight (metal plates built into the back combined with the engine weight), contribute to its operation. The load lifted by a forklift cannot exceed the weight of the counter-balance, otherwise it will tip the forklift forward.
The wheels and axles also help to keep the forklift stable. The front two tires and the center of the rear axle create what’s called the “stability triangle”. The forklift’s balance point (the center of gravity between the load and the counterweights) has to be kept within this “triangle”.
Forklift Basic Principles – a video describing the stability triangle
Forklift Trucks – Wiki includes an explanation of these counterbalance parts
How Forklifts Work – a guide to the basics of forklifts
Forklifts 101 – a slide show that discusses counterweights and other basics
The crane is another good example of how simple machine principles are applied today. The crane makes use of the pulley to move heavy materials upwards, move them horizontally to another location, and then lower them. Some cranes are stationary towers that are erected, used, and then disassembled, while others are on a movable base that can be driven to other locations.
What is a Crane – a look at how simple machines make a crane work
How Does a Crane Work? – eHow takes a look at how cranes function
How Tower Cranes Work – a closer look at tower cranes
How a Crane Stays Balanced – discusses the principles of the counterweight
While these machine concepts may be seem simple, they’re also rather “intelligent” in the ways their principles greatly enhance modern capabilities. They’ve shaped technological advancement and human history -and without them, we wouldn’t be able to accomplish the many tasks we may take for granted, such as building tremendous structures and lifting, transporting, and even storing extremely heavy loads.