A falling cube and equivalent pulley systems
The centre of gravity in free fall, and pulley trains of equal ease
At the upper right a cube is drawn tumbling in successive positions along a vertical track, illustrating Leonardo's claim that the accidental centre of gravity of a freely descending body stays concentric with the central line of its motion, even as the body rotates. The rest of the sheet works through pulley arrangements: a train labelled a b is said to move as easily as one labelled c d, each carrying weights of 8, and a further system below is noted to behave like those above.
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Centre of gravity of a freely falling body
The accidental centre of gravity that freely descends will always be concentric with the central line of its motion, even though the falling weight should rotate during its descent.
Equivalent pulley systems
Two pulley systems each carry weights of 8: the motion of the train labelled a b is as easy as that of the one labelled c d. A further pulley system drawn below is said to behave in the same way as those above.