The Revolving Arm and an Experiment on the Lines of Motion
A body flung from a pivoted arm follows a quarter-circle; dropping a clay ball to trace its path
Propositions on percussion and on bodies thrown by a revolving arm, with an experimental note. Leonardo states that fragments struck off by a round body radiate from the center of the struck place, that a blow in resonant bodies is felt at once throughout, and that a body flung from the end of a pole-mounted arm is accompanied by its mover for no more than a quarter of the circle. A closing paragraph describes a method (points a, m; figure 14) for experimenting with the lines of motion: placing a ball of fresh clay at m on an ashed spot, letting it descend along a rule, and marking on the floor where the various throws strike.
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Struck-off fragments radiate from the center of the blow
Things struck off from their remainder by a round body follow courses whose lines are caused from the center of the struck place. A blow in resonant bodies is felt immediately throughout the whole struck body.
A body flung from a pole-mounted revolving arm
A body resting on the extremity of a piece of wood that turns upon a pole is accompanied by its mover no more than a quarter of the circle made by the revolution of the wood's head. The flung weight then follows a great part of its course along the chord found in that quarter-circle.
Experiment: tracing the lines of motion with a clay ball
At m, place a ball of fresh clay on an ashed spot and note on the floor where it strikes; mark at a the line of the throw, letting it descend along a rule. At m are drawn the lines of the thrown thing; at a, the lines of the various descending blows.