How do multiple pulleys make it easier to lift a heavy load?

Multiple pulleys make it easier to lift a heavy load by creating a mechanical advantage, which allows a smaller input force to lift a greater weight. This system, often called a block and tackle, uses a combination of pulleys and a flexible rope or cable to distribute the load across multiple segments of the rope.12

When you use a block and tackle, the force required to lift the load is reduced because the distance over which you must pull the rope increases. For example, if a load is supported by four segments of rope, you must pull four feet of rope to lift the weight one foot. In this scenario, the force magnification is four, meaning you only need to exert a fraction of the effort that would be required to lift the weight directly. While adding more pulleys can further increase this mechanical advantage, the benefit is eventually limited by the increased friction within the system.1