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Adiel Fernandez presents several examples of activities dealing with 
so-called simple machines but also perpetuates a common mistake. A wheel used for 
rolling something—such as a wheelbarrow or the wheels on a car—is NOT a 
simple machine. It is a device for reducing friction, and a very useful device 
at that. The wheel-and-axle, which IS a simple machine, is like the steering 
wheel of a car or any crank. It is essentially a lever which can go round 
and round on its fulcrum or pivot. The name is unfortunate because for many 
people, including some textbooks, it leads to this mistake. For the 
wheel-and-axle the basic law of simple machines holds: the applied force times 
distance moved equals the output force times distance moved. For the rolling wheel 
this does not apply. 

Ted Ansbacher
Science Services
29 Byron Ave, White Plains, NY 10606
Tel: 914-328-5407 • Fax: 914-328-5407
[log in to unmask] • www.scienceservs.com

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