Tension in a loaded cord and pressure in a water cistern
How a weight on a horizontal cord loads its ends; a weight pressing on water
The page pairs two force studies, drawn with balances, pulley systems and a cistern. Leonardo shows that a weight of 4 pounds hung at the middle of a level cord loads each end only lightly when the cord sags (a b), but with more than a hundred pounds when the cord is nearly straight (c d) — warning the reader not to abandon experiment lest he be deceived. He notes that the same rule serves for pushing as for pulling. A final figure and note (peso che preme, aria, acqua) state that a weight pressing on a water cistern pushes proportionally on every part of it, just as the water did by itself.
On this page
A weight at the middle of a level cord
The more a weight at the middle of a level cord bends it, the less it burdens the ends, and conversely. Four pounds hung at the outermost bendings, as a b shows, give each perpendicular side half the weight; but the same 4 pounds at the middle of a level cord make each side feel more than a hundred pounds, as shown in c d.
The same rule for pulling and for pushing
The rule you use to find the nature of pulling you will also use in the nature of pushing.
A weight pressing on a water cistern spreads its force everywhere
The weight that presses upon the water-cistern pushes proportionally in all parts of that cistern, in the same manner and proportion as the water alone did before. For example (verbigratia).
Confirm the figures by experiment
These two figures are shown to be almost of one and the same nature; yet do not leave experiment behind, so that you not be deceived.