On flyers: pulleys, falling bodies, and bird flight
Rope velocities in a tackle, and how a bird's spread changes its weight
Headed 'On flyers', the sheet joins a long analysis of ropes running through a system of pulleys to a study of falling bodies and the flight of birds, with small margin figures of a tackle, an oblique front, and a group of birds. Leonardo works out how the velocities and loads of the cords in a tackle depend on their number and on the excess of the mover, and why the first cord breaks at the highest point of its straightness. He then applies the guiding role of the heaviest part to bodies falling obliquely, argues that a bird cannot rest on the air at any degree of obliquity, and concludes that a bird spreading itself more weighs less.
On this page
Rope velocities and loads in a system of pulleys
The cords of one tackle have as many speeds as their number, and those descending to draw the weight up are faster than those rising. The mover is always stronger than the moved; immovable cords carry double the weight (load plus resistance), and when excess equals the weight the cords feel four times it. The first cord always breaks at the highest point of its straightness, where it leaves the pulley.
An oblique front falls heavier than the whole body plumb
The front a b is heavier falling obliquely than the whole body falling perpendicularly, because that front makes itself the guide of the motion with all the power the weight has by its obliquity.
Degrees of obliquity: a bird cannot rest upon the air
The degrees of obliquity must be calculated, because at no degree of obliquity does the bird stop upon the air; it grows swifter or slower as the obliquity is less or more oblique, as the water shows outside the site of equality.
A bird that spreads more weighs less
The bird that spreads itself more weighs less, and conversely the one that occupies less space becomes heavier.