A windmill is a machine that uses the wind to turn a wheel of adjustable vanes, slats or sails. As the wheel turns, it turns a shaft, wheels, and gears that power machinery. It is more properly called a “wind pump,” but most people call it a “windmill.” Windmills have been used for hundred of years to power machinery used to grind grain such as wheat and corn. Today we also have windmills, called “wind turbines,” that generate electricity.
All machines are a combination of several simple machines or modifications of one. A simple machine is one that is moved by just one force. The six types of simple machines are the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw. A lever is a long plank, beam or bar that is used to move heavy loads. Examples of a lever are seesaws, scissors, broom, tweezers, and ice-tongs. A wheel is a cylindrical object that rotates about axis of the cylinder. Wheels are on cars and trains. Some wheels turn other wheels, like geared wheels on a bicycle or a clock. Some wheels turn together like the doorknobs, or the knobs on a televisions. A pulley is a grooved wheel. A rope is fitted into the grove and turns the wheel when pulled. An inclined plane is a very simple machine. It has a sloping surface that makes it easier to pull, push, or roll heavy objects. Examples are wheelchair ramps or a stairway. The screw is an inclined plane wound at its edge on a cylinder or cone. Examples of a screw includes faucets,
screw-in bulbs, and screw-on bottle tops. The wedge is essentially an inclined plane such as knives, blades, nails, needles, pins, wood and axes.
The wind or running water forces the big blades of a windmill or water wheel to turn (wheel and axle). By bending the axle and attaching a lever, the rotary motion becomes an up and down motion, which can make a pump handle go up and down. By adding gears to the turning axle, the force or speed can be increased and used to grind grain, drive looms, or sharpen knives.