Friction and the motion of weights over planes
How a thinner axle eases motion; how a suspended 8-pound load splits between two supports
Leonardo opens with the science of friction and moving weights, noting that the thinner the axle of wheels drawn across a surface, the more easily they move, and that friction varies with the surfaces in contact. Two pulley-and-cord diagrams with hanging weights illustrate the point at the top of the sheet. Below, a large circle inscribed in a triangular frame analyses how a suspended body of 8 pounds discharges 4 pounds onto each of two supports (f and r), demonstrated by a central line a m meeting the horizontal r n at point a.
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Thinner axles ease the motion of wheels
The heading treats the motion of a weight together with its contact and friction. Leonardo states that the thinner the axle of wheels drawn over flat surfaces, the more easily motion is rendered to whatever drives them.
Friction varies with the surfaces in contact
The frictions produced by heavy bodies cost their movers efforts that vary in proportion. That variation follows from how varied the surfaces of the bodies are where they touch.
An 8-pound load split evenly onto two supports
A suspended body of 8 pounds discharges 4 pounds onto f and 4 onto r, shown by the central line a m that ends at the midpoint a of the horizontal line r n. Leonardo adds that resting on the point c does as much as being sustained at v, since each line acquires 4 of the total 8 pounds.