Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.
A block and tackle with four pulleys would have a mechanical advantage of:
2 |
|
0 |
|
1 |
|
4 |