On the cord: a weight at the center of a horizontal rope
The loaded cord can never be pulled straight; force lives and dies with the potential lever
Under the heading 'On the cord' Leonardo states that a horizontal cord bearing a weight at the middle of its length can never be straightened, whatever its thickness or strength. He develops the geometry of the 'potential angle', which is always right, set against the real angle that may be acute, right, or obtuse. A further section on the resistance of the arched cord concludes that force is born together with the potential lever, grows as that lever shrinks, and dies when it fails; diagrams at the right show a loaded beam, an arched cord, and a cord carried over pulleys with a hanging weight.
On this page
A loaded horizontal cord can never be straightened
A cord of any thickness or strength, set horizontal in the site of equality, can never have its opposite ends pulled straight while a weight hangs at the middle of its length. The upper right of the sheet shows such a horizontal member with a weight hung below it.
The potential angle is always a right angle
The potential angle is always right and lies either outside or inside the real angle, which is obtuse or acute. Only when the real angle is itself right does it unite with the always-right potential angle.
Force is born and dies with the potential lever
Given a straight cord that just breaks under its own weight at its attachment, Leonardo asks what weight it will bear once arched with its ends level. Wherever the potential lever exists, force exists; force is greater the smaller the lever, and it dies when the lever fails. The lower right shows the arched cord carried on pulleys with a hanging weight.