<P> The wheel and axle can be viewed as a version of the lever, with a drive force applied tangentially to the perimeter of the wheel and a load force applied to the axle, respectively, that are balanced around the hinge which is the fulcrum . The mechanical advantage of the wheel and axle is the ratio of the distances from the fulcrum to the applied loads, or what is the same thing the ratio of the diameter of the wheel and axle . A major application is in wheeled vehicles, in which the wheel and axle are used to reduce friction of the moving vehicle with the ground . Other examples of devices which use the wheel and axle are capstans, belt drives and gears . </P> <P> The Halaf culture of 6500--5100 BCE has been credited with the earliest depiction of a wheeled vehicle, but this is doubtful as there is no evidence of Halafians using either wheeled vehicles or even pottery wheels . </P> <P> One of the first applications of the wheel to appear was the potter's wheel, used by prehistoric cultures to fabricate clay pots . The earliest type, known as "tournettes" or "slow wheels", were known in the Middle East by the 5th millennium BCE (one of the earliest examples was discovered at Tepe Pardis, Iran, and dated to 5200--4700 BCE). These were made of stone or clay and secured to the ground with a peg in the center, but required effort to turn . True (freely - spinning) wheels were apparently in use in Mesopotamia by 3500 BCE and possibly as early as 4000 BCE, and the oldest surviving example, which was found in Ur (modern day Iraq), dates to approximately 3100 BCE . </P> <P> Evidence of wheeled vehicles appears in the second half of the 4th millennium BCE, near - simultaneously in Mesopotamia (Sumerian civilization), the Northern Caucasus (Maykop culture) and Central Europe (Cucuteni - Trypillian culture). </P>

How does a wheel and axle increase force