Machines are used by humans to help them do work. Simple machines are used to lower the amount of force needed to do work or change the direction of a force. If less force is applied, the force must be applied over a longer distance.
Force is a push or pull.
Simple machines are trading distance for force.
The amount of work done is always the same - scientists call this conservation. This means that to do the same amount of work, someone can either exert a lot of force over a small distance or a little bit of force over a big distance. The equation "work = force x distance" works great on paper; however, in the real world this isn’t precisely true. The truth is, when we use simple machines we introduce friction. Therefore, the amount of work done is a little bigger using a pulley to lift something (small force, big distance) than just lifting it by arm (big force, small distance). The trade-off is still in effect, but because of friction there is a slightly larger amount of work involved.
© S. Olesik, WOW Project, Ohio State University, 2001.
Print Version Simple Machines Experiments Main Experiments Page Home