On Motion and the Moving Body: Power Versus Motion
Derivative motion proportional to primitive; the oxen-drawn cart as proof of dependence
This text page poses the question of which drives a moving body further: a great power with little motion, or a lesser power with greater motion. Leonardo answers that the derivative motion is longest where the primitive motion given by the same mover is greatest, citing a proposition that the lengths of derivative motion stay in the same proportions as their primitive motions, so that a power moving a body one finger in one 'harmonic time' will move it two fingers in two such times. He adds that impetus is not always generated in the moving body, because the mover itself does not always move impetuously. The point is illustrated by a light cart drawn by oxen on level ground, which stops the instant the oxen stop.
On this page
Great power with little motion versus lesser power with more
The derivative motion of a given body is longest when its primitive motion from the same mover is greatest. Experience shows a single power keeps a fixed proportion between its primitive motion and the derivative motion of its body, so the lengths of derivative motion follow the same proportions as the primitive motions that cause them.
The oxen-drawn cart: motion ceasing with its mover
Impetus is not always generated in a moving body, because the mover itself does not always move impetuously. The light cart drawn by oxen on level ground shows this: the moment the oxen end their motion, the cart's motion is ended too.
