The Counter-Lever and the Rebound of Struck Balls
Propositions on motion and percussion, with a small lever-and-weight device and rows of round bodies
A page of terse propositions on motion (moto) and percussion (colpo). Leonardo argues that a body thrown by a blow is least accompanied by its mover, that a counter-lever hurls its weight farther the shorter its arm, and that struck round bodies rebound at equal, opposite distances along the same lines when the angles are equal. A small T-shaped lever-and-weight device is drawn at the right, with two rows of round balls (numbered 29 and 30) illustrating the percussion cases.
On this page
The counter-lever (contralieva) and the length of its arm
A counter-lever will hurl its weight farther and faster the shorter its lever-arm. Struck at the middle of its length by the violence of a blow, it throws the weight set upon it more quickly and farther than a blow delivered at the quarter of its rise against a strong, resistant object.
Two opposite bodies produce two equal opposite bounces
The blow born from two opposite motions made by bodies of equal course and quality causes two equal opposite bounces, at equal distance from the site of their percussion.
Three round bodies striking together rebound symmetrically
If three round bodies of equal quality and motion strike one another together, the rebound is of equal distance from the place of percussion and along the same lines that created the blow, the angles of percussion being equal.