If I lift a 100kg weight using a rope over a pulley and the distance that I pull the rope down is equal to the distance that the weight is lifted then I am lifting 100kg, right.
But now if I am tied to a rope which is looped over a pulley and I pull on the other end of the rope to lift myself (with the same 1:1 mechanical advantage as before) then am I still pulling 100kg? I am thinking that I am now pulling 50kg... is that correct?
Dear will_usher:
Assuming you are 100 kg, your arms will support 50 kg, and since the tension in the rope is the same everywhere with a pulley, then where it is tied will support the other 50 kg.
Yes.
David A. Smith
I am not sure if I can picture what you are saying. It sounds like you do have the 1:1 mechanical advantage, which means if you want to lift 100 kg, you need to pull with 100 kg. If you have a proper block and tackle set up, the easiest way to figure out your mechanical advantage is to count the number of rope segments going between the two pulleys.
You should remember that the free end will also have to move a lot.
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