The Chair Lift

You can lift yourself with the aid of a block and tackle. We use five pulleys here, one of which is used only to change the direction of the force. Each one of the other four pulleys halves the force that is needed to lift the person sitting on the chair. This means that you only have to lift one sixteenth of your weight, but you have to pull the rope a distance that is 16 times longer. This is the "golden rule" of mechanics: "What you win in force you have to pay for in travel".