Machines help us in two ways:
1. By reducing the amount of force on an object.
2. By changing the direction of the force.
Throughout history, humans have developed several devices to make work easier. The most notable of these are known as the "six simple machines": the wheel and axle, the lever, the inclined plane, the pulley, the screw, and the wedge, although the latter three are actually just extensions or combinations of the first three.
Because work is defined as force acting on an object in the direction of motion, a machine makes work easier to perform by accomplishing one or more of the following functions, according to Jefferson Lab:
transferring a force from one place to another,
changing the direction of a force,
increasing the magnitude of a force, or
increasing the distance or speed of a force.
Simple machines are devices with no, or very few, moving parts that make work easier. Many of today's complex tools are just combinations or more complicated forms of the six simple machines, according to the University of Colorado at Boulder. For instance, we might attach a long handle to a shaft to make a windlass, or use a block and tackle to pull a load up a ramp. While these machines may seem simple, they continue to provide us with the means to do many things that we could never do without them.
Wheel and axle
The wheel is considered to be one of the most significant inventions in the history of the world. "Before the invention of the wheel in 3500 B.C., humans were severely limited in how much stuff we could transport over land, and how far," wrote Natalie Wolchover in the Live Science article "Top 10 Inventions that Changed the World." "Wheeled carts facilitated agriculture and commerce by enabling the transportation of goods to and from markets, as well as easing the burdens of people traveling great distances."
The wheel greatly reduces the friction encountered when an object is moved over a surface. "If you put your file cabinet on a small cart with wheels, you can greatly reduce the force you need to apply to move the cabinet with constant speed," according to the University of Tennessee.