There are six main simple machines: Lever, Wheel and axle, Pulley, Inclined plane, Wedge and Screw. This essay explains how I use three of these almost everyday.
A lever is a simple machine that consists of a beam, a plank or a rod pivoted at a point on a hinge called a fulcrum. The fulcrum provides leverage which is used to life heavy loads with only a small force. You can see the lever at work on the playground as a seesaw.
The wheel and axle is a simple machine where both are attached to each other so that they rotate together. Think of a bicycle wheel or a Ferris wheel. The axle is attached to the larger wheel with spokes. When the axle rotates, the large wheel rotates at the same time and in the same direction.
A screw is a simple machine that consists of a shaft that has grooves which are called threads. The threads are cut into the shaft which makes it easier to force the shaft into any type of material like wood or metal. A rotational force is used to fasten objects together. For example, screws are used in everyday life to secure doors in place, hold furniture together or secure outlets on a wall. I go around the house with a screwdriver tightening screws.
These simple machines may have been inventions in ancient times, but I use them to have fun!