On Mover and Moved: Lever and Counter-Lever
The power of the mover always exceeds the resistance of the moved
Headed 'De motore e mobile' (On the mover and the moved), this page treats the lever with text and three marginal sketches: two rods joined at a fulcrum, a wedge-shaped figure with parallel lines, and a horizontal balance-arm carrying hanging weights. Leonardo states that the power of the mover is always greater than the resistance of the moved, and that at the ends of a lever and counter-lever the motion of the mover exceeds that of the moved in proportion as the moved has the greater natural weight. He proves the point by tracing the motion of the mover from b to d and that of the moved from a to c.
On this page
The mover's power exceeds the moved's resistance
The power of the mover is always greater than the resistance of the moved. At the end of the lever the motion of the mover exceeds the motion of the moved at the counter-lever by as much as the moved is of greater natural weight.
Accidental versus natural weight at the lever's ends
As much accidental weight is added to the mover at the end of the lever as the moved at the end of the counter-lever exceeds it in natural weight. The motion of the mover is greater than that of the moved by as much as the mover's accidental weight exceeds its natural weight.
Proof by the motions b-d and a-c
Let the motion of the mover be from b to d and that of the moved from a to c. The motion b d is greater than the motion a c by as much as the accidental weight of b exceeds the weight b, which it exceeds by one; therefore also by the natural weight.