A block and tackle gives us mechanical advantage because each section of rope used in the system shares the load. If there are two ropes (as in a simple moveable pulley setup), each rope carries half the load. A simple moveable pulley gives you a mechanical advantage of 2. Used together, there can be many ropes and several wheels. The mechanical advantage of the setup will be the number of sections of rope that are holding the object (don’t include the one you are pulling on).With a mechanical advantage of 2, such as in a simple block and tackle with one fixed and one moveable pulley, you only have to pull with half as much force as the weight of the object. But there’s a catch! Here we go again: work = force x distance. If you’re getting the same amount of work, with only half the force, what has to change? The distance doubles. The amount of rope that you’ll be reeling in is twice as much with this system. It will increase with each pulley that you add, and the force will decrease by that amount also.
