I bumped into this interesting question while looking for a fun mechanical black-box puzzle:

Pulling the rope with one hand is as heavy as with two hands?

I wonder if it is possible to generalize this puzzle somehow, say, needing to exert 10N of force with each hand to single-hand pull the inside object up (just translating upward without rotating), but if using both-hand pull, then the force on each hand would be higher (say, 20N) or something.

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    $\begingroup$ Please put all details from the previous puzzle that are needed to solve this one within the question itself $\endgroup$
    – bobble
    Commented Mar 7, 2022 at 16:32

1 Answer 1


This small adjustment should do the trick, even though it won't be linear:

enter image description here

When you pull on a single rope, you'll of course get the mechanical advantage of the centre of the pulley only moving half the distance of the pull.

But the pulley is now big, and the weight attachment point is above the centre of the pulley, so a single rope pull will gain extra mechanical advantage as the pulley turns, making the attachment point move downwards relative to the centre of the pulley.


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