Intentional combustion.

There are many ways in which machines, both simple and complex, help to make everyday tasks more manageable.  Simple machines include the lever, wheel and axle, pulley, inclined plane, wedge and screw.  Complex machines are merely assemblies of many simple machines as well as purpose-specific parts designed for how the machine is intended to be used, such as bar and chain assemblies for a chainsaw or a long crankshaft and gearbox for a weed trimmer.  Chances are good that you have already seen simple and complex machines at work today such as a weed trimmer, chainsaw, lawnmower or automobile.  Watch the video above to get a brief introduction to a two-stroke engine's combustion cycle then consider how it is implemented in a device that you have used.