A "Pulley" and a "Wheel and axle" seem much similar to each other. What is their actual difference and what are their precise definitions?
My understanding of the two terms is much relied on the context of Simple machines. The wikipedia articles of the two terms provide a definition which makes them seem very similar. But since simple machines are considered (by ancient greeks) as six distinct different basic machines then they must have an important difference.
I'm not sure, but maybe modern treament of mechanical machines in terms of "Linkage synthesis" could give a better explanation. If it's possible, please explain the differences and the definitions both in the context of "Simple machines" and "Linkage synthesis" methods.