How much weight does it require to lift 100 lbs with 4 movable pulleys?

To lift 100 lbs using a system of 4 movable pulleys, the mechanical advantage provided by the pulleys is key. Each movable pulley effectively halves the weight you need to lift. Therefore, with 4 movable pulleys, the required effort to lift 100 lbs would be approximately 100 lbs ÷ 4 = 25 lbs. Thus, you would need to apply about 25 lbs of force to lift the 100 lbs load.