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Mechanics.

a Body passes over equal Spaces in equalTimes. Accelerated Motion is that whichis continually augmented or increased; asRetarded Motion is that which continuallydecreases : And if the Increase or Decreaseof Motion be equal in equal Times, theMotion is then said to be equably acceleratedor retarded (XXI).

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it much greater than it really is, whereas if he rideswith it , he finds it less.

Scholium.

6. The Reason of all these different Phænomena ofMotion will be evident if we only consider, that we mustbe absolutely at Rest, if we would discern the true orreal Motion of Bodies about us. Thus a Person on theStrand will observe the Ships failing with their real Ve- :locity ; a Person standing still will experience the true .Strength and Velocity of the Wind ; and a Person pla-ced in the Regions between the Planets will view all theirtrue Motions; which he cannot otherwise do, because ;in all other Cafes the Spectator’s own Motion must beadded to, or subducted from, that of the moving Body;and the Sum or Difference is therefore the Apparent orRelative Motion , and not the True.

(XXI) i. Equable Motion is generated by a singleImpetus or Stroke; thus the Motion of a Ball from aCannon is produced by the single Action of thePowder in the first Moment, and therefore the Ve-locity it first sets out with would always continue the jfame, were it void of Gravity, and to move in an un-resisting Medium, which therefore would be alwaysequable, or such as would carry it through the fameLength of Space in every equal Part of Time.

2. Accelerated. Motion is produced by a constant Im-pulse, or Power which keeps continually acting uponthe Body, as that of Gravity, which produces the Motionpf Falling Bodies, which Sort of Motion is constantly2 accelerated,