Some simple machines are a wheel, a pulley, a lever, a screw, and an inclined plane.
Harder - Most machines consist of a number of elements, such as gears and ball bearings, that work together in a complex way. No matter how complex a machine, it is still based on the compounding of six types of simple machines. The six types of machines are the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw. Here you can find the answers to some commonly asked questions about simple machines. Also provides a brief introduction to uses of a gear, cam, crank and rod, chain and belt, and the ratchet.