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The Universe
Fifth. If a force move a body in a certain time a certain distance it is not necessary that such power move twice this weight in twice the time twice this distance, because it might be that this force could not move this body. Sixth. If a force move a body in a certain time a certain distance, it is not necessary that half of this force move this same body in the same time half this distance, for perhaps it would not be able to move it. Seventh. If two separate forces move two separate bodies the same forces united will move in the same time the two movable things joined together for the same distance, because the proportion remains the same.110 Nothing that can be moved is more powerful in its simple movement than its mover.111 Of the mover or the movable thing The power of the mover is always greater than the resistance of the thing moved.112 Of the movement made by things proportionately to the power which drives them One ought to make the experiment with a crossbow or other power which does not grow weaker, and also with balls of equal shape and of different substances and weight to test which goes furthest away from its motive power, and to test with various shapes of various sizes, breadths and lengths and to make a general rule. I wish to know what weight the power will have which shall drive to a greatest distance from itself a weight of a pound spherical in shape.113 Of the power of the crossbow The weight that charges the crossbow has the same proportion to the weight of the arrow as the movement of the arrow of this crossbow has to the movement of its cord. Here one ought to deduct three resistances made by the air, that is the percussion of the bow of the crossbow made