Simple machines are "simple" because most have only one moving part. Some are so simple, they don't have any moving parts! When you put simple machines together, you get a complex machine, like a lawn mower, a car, even an electric nose hair trimmer! Remember, a machine is any device that makes work easier. In science, "work" means making something move.
It's important to know that when you use a simple machine, you're actually doing the same amount of work — it just seems easier. A simple machine reduces the amount of effort needed to move something, but you wind up moving it a greater distance to accomplish the same amount of work. So remember, there's a trade–off of energy when using simple machines.
Today you will start research on one of these topics about simple machines::