Curated OER
Integrated Publishing/block & Tackle (Or Pulley)
Very substantial four-page article on how the block & tackle works. (It's a simple machine -- a pulley.) Lots of illustration. Mechanical advantage, formulae, solved problems, all here. Good source for info.
Curated OER
Integrated Publishing/the Screw
A full and complete discussion of the simple machine called the screw, a modified inclined plane. Many examples and drawings and applications.