WHEEL AND AXLE
A wheel and axle is a simple machine consisting of a wheel and axle. A wheel and axle adjusts the force-distance ratio by having an input force applied over the distance of a circle with a large diameter (the wheel) focused into a greater output force over the distance of a circle with a smaller diameter (the axle). You can calculate the mechanical advantage of a wheel and axle by dividing the radius of the wheel by the radius of the axle.
A classic example of the wheel and axle at work is the winch used in water wells to raise and lower the bucket. The heavy bucket of water requires a fairly large amount of force, and this force is then exerted over the small distance of the radius of the axle. When turning the the attached, longer handle (the wheel) you are exerting your force over a greater distance, therefore making it so that less force is required on order to do the same amount of work.