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Pulley Basics
Here are some animated drawings of a fixed pulley and a movable pulley. Then, of course, there is the combined pulley which makes life even more easier.
TeachEngineering
Teach Engineering: Powerful Pulleys
Learners continue to explore the story of building a pyramid, learning about the simple machine called a pulley. They learn how a pulley can be used to change the direction of applied forces and move/lift extremely heavy objects, and the...
Walter Fendt
Walter Fendt: Sistema De Poleas
This site is an interactive applet using the principles of a pulley system. The number of pulleys can be varied as well as the load lifted