Two Weights on a Cord Thrown Through the Air
Primitive and derivative motion defined, with a crossbow and a catapult as launchers
The sheet studies two moving bodies thrown through the air while joined to the opposite sides of one cord, and defines its terms: primitive motion is that made while the body is joined to its mover, derivative motion is that made through the air after separation, and the derivative never matches the velocity or power of the primitive. Beside a sketch of a crossbow with cord and weights, Leonardo notes that the body's course follows the straightness of its mover's course when all its parts share the primitive motion. A catapult loaded with balls illustrates that when all parts move equally the body does not rotate, receives the mover's full power, and travels its due length, provided its weight is proportioned to the mover's power. A margin note asks for that proportion of weight to be determined.
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Primitive and derivative motion defined
Primitive motion is that made by the body while joined to its mover; derivative motion is that made through the air once separated from it. The derivative derives from the primitive but never has velocity or power equal to it.
A straight course when all parts move equally
The body's course conforms to the straightness of its mover's course when all its parts share the mover's primitive motion. If all parts move equally the body will not rotate, will receive the mover's entire power, and will keep its due length of travel when its weight is proportioned to that power.
Crossbow and catapult as launching apparatus
The dynamics are illustrated with a crossbow drawn with its cord and weights, labelled a, and a catapult loaded with balls, labelled a b. These launching devices serve to project the coupled weights whose motion the note analyses.