machine · effort · energy · invent · tool
A simple machine is a basic tool that helps us do work. Simple machines have very few moving parts. They make it possible to do more work with less effort and less energy. Long ago, people invented simple machines to help them build cities, sail oceans, and transport heavy loads. There are six types of simple machines: the inclined plane, the lever, the wedge, the screw, the wheel and axle, and the pulley. These tools are around us every day and make our lives much easier. Many complex machines are built by combining two or more simple machines together.