Regardless of their complexity, all machines utilize some or all the components of simple machines to function. A child’s red wagon offers an excellent example of a wheel-and-axle simple machine. Simple machines are mechanical devices that apply a force and include a lever, inclined plane, wheel and axle, screw, wedge and pulley. With little moving parts, these simple machines make life much easier when you require help working on a project. When combined, they create complex machines with many moving parts.

Simple machines basically operate by transmitting mechanical labor from one part of the device to another. Simple machines generate force and control its direction and motion but do not make energy. Two factors measure the functioning of a simple machine: it’s mechanical advantage and efficiency. Mechanical advantage equals the ratio of the force employed by the machine to the force applied to it. No machine works harder than the force put into it. A simple machine’s efficiency is a measurement of the ratio between the work put into it and the work it puts out.

The center of the axle serves as a fulcrum for the wheel. An axle simple machine is essentially an adapted lever, but it moves a load farther than a lever does. When a bar rests on a pivot point, you apply force to one end of the lever. With the fulcrum or pivot point in the right location, it can move the load a few inches or feet. But as a modified lever, the wheel and axle simple machine can move the load across miles, depending on the energy source. The ratio of the radii of the wheel and axle define the ideal mechanical advantage of the device.