# Simple Machines

Human evolution started with the help of very basic primitive devices. This article provides detailed information regarding simple machines, which have been used since ancient times.
Human beings work their entire lifetimes for just one thing - to make life easier. All old inventions, as well as new ones are a result of this motive. The various machines that are used today have their basis in simple tools or machines. Few machines were invented to make our tasks easy to accomplish. They used energy to work, and were made of a few or no moving parts.

History
Tools have been in use since the Stone Age. Man used stones, sticks, teeth, etc., to complete his daily work. As time passed, these tools became more sophisticated. In the 3rdcentury BC, Greek philosopher Archimedes came up with the idea of simple tools or machines, such as lever, pulley, and screw. However, his knowledge was limited to static balance of force, and he didn't explain the relation between force and distance. In 1600 AD, Italian scientist Galileo Galilee, explained the dynamic theory of simple machines, in his book Le Meccaniche, and was the first person to explain that these machines do not create energy, but only transform it. By then, the 'Archimedean' group of simple machines also included the wedge.

Six Types
A simple machine is a device that helps in performing a task by transforming energy, between the force applied and the distance over which it's applied. The following is a list of six machines that have been in use for centuries:

Lever
Its name has been derived from the French word lever, which means 'to raise'. The lever is a rigid object, like a bar that turns (pivots) against a turning point (fulcrum) to pry something loose. The object moved by the lever moves is called 'load', and it is easier to move, if the object is closer to the fulcrum. The curved arm or claw-end of a hammer is called a lever. When you rest it against the surface of the wall (fulcrum), and rotate it using force, it pulls the nail out from the wall. There are three subtypes of levers, depending on the varied locations and the force applied:
• First-Class Lever: In this type, the fulcrum is located anywhere between the input force and the output load. Bicycle hand brakes, see-saw, and scissors are some examples of these levers.
• Second-Class Lever: In this kind, the input force that has to be applied, is located at the end of the bar, and the fulcrum is at the opposite end, with the output load between these two forces. Some examples are tennis racquet, paddle, etc.
• Third-Class Lever: In this type, the input force applied is higher than the output load, but the distance that the load moves is more than the distance moved by the force. As both the motions occur in the same time duration, the load moves faster than the force applied. Shovel, tongs, human hand, etc., are some examples of the third-class lever.
Inclined Plane
A plane is flat surface. When it's slanted, it is called an inclined plane. This type is used to either raise or lower an object. The working mechanism of this machine is very simple, a large load can be moved by applying a small force, through a longer distance. For example, less force or effort would be required to move an object on the ramp than a straight surface, as less energy is used to move an object with an inclined plane. Slides and ramps are some examples of an inclined plane.

Wedge
It is made of two inclined planes, which unlike a single inclined plane does not remain static, but moves. When two inclined planes meet, they form a sharp edge, which is used for splitting, cutting, holding, and dividing objects. It is triangular in shape. More force has to be applied to a short wedge with a wide end, than a long wedge with a narrow end. A fork, knife, fan, teeth, etc., are some examples of a wedge.

Screw
An ancient Greek mathematician called Apollonius of Perga, in 200 BC had worked out the concept of spiral-helix (coiling). Screw is a helical inclined plane, which is based on this concept, and can convert a rotational force into a linear force and vice versa. The helical is formed on one end of an inclined plane, and the provision to turn it is on the opposite end. They are available in different shapes and sizes, and their main purpose is to hold or fasten objects together and raise weights. However, a screw depends upon another machine, like a lever for its operation.

Wheel and Axle
They are levers that are rotated in a circle around the fulcrum. The axle is a rod that goes through the wheel and helps in rotating it. The rod or rope that turns the wheel converts the rotational motion into a linear motion for the purpose of either lifting or moving forward an object. The larger wheel rotates around the smaller axle. Cars, roller skates, gears in clocks and bicycles, etc., are some examples of this machine.

Pulley
This machine is a variation of the wheel and axle, wherein the wheel rotates the rod or rope instead of the pulley. In this device, one part of the cord is attached to the load or object, and another on the wheel. As you pull on one side, the wheel rotates, moving the load forward or backward. The distance from which the force is applied and distance that the load moves are different, but the operating work involved is the same. A pulley is used to move things that are hard to reach. Flag poles, blinds, and cranes are some examples of a pulley.

Most of the machines that we use today are based on the mechanics of these six simple machines. More complicated machinery is called a compound machine, which is made up of two or more simple machines. These types make work easier, efficient, and faster to complete, and are easy to operate.