Force, Weight and Impetus in the Crossbow
The primary and derivative motions of the bolt, a pendulum note, and mechanical devices
This sheet reasons about the relationship between force and weight in the crossbow or balista, arguing that the bolt's motion stands to the motion imparted by the cord as the loading weight stands to the arrow's weight, and that when force is the cause of a weight the weight can never surpass the force. A small pendulum figure carries the maxim that motion produced by impetus is never equal to the original because it is accidental. Around the text are drawn mechanical devices — dividers, a framed screw-and-lever mechanism, and a trussed lifting frame — which the transcription does not caption.
On this page
Primary versus derivative motion, force versus weight
Measuring the primary motion by the derivative, Leonardo finds the same proportion between them as the weights that caused the motions once had: the bolt's motion is to the motion the cord gave it as the weight loading the crossbow is to the weight of the arrow. When force is the cause of a weight and both are of equal motion, the weight is less than or equal to the force and can never surpass it — less when a great weight moves the cord only a finger and then touches ground, equal when it hangs in the air on the cord.
Motion from impetus is accidental
Beside a small pendulum swinging in the upper right corner, a note states that the motion made by impetus will never be equal to the first, because it is accidental. It marks the loss inherent in a motion that is derived rather than original.
Drafting instruments and a framed screw mechanism
The upper part of the sheet carries drawn dividers or compasses and a framed mechanism of screw and lever set within a rectangular housing. These devices are shown without captions among the geometric and mechanical studies of the leaf.
A trussed frame for lifting
At the right a triangular trussed structure is drawn, of the kind used to raise or support a heavy load. It appears among the mechanical sketches surrounding the text on force and weight.