The Laws of Motion on Superphysics

The Laws of Motion

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Law 1

Every body perseveres in its state of rest, or uniform motion unless it is compelled to change that state by external forces impressed on it.

PROJECTILES persevere in their motions so far as they are not retarded by air resistance, or impelled downwards by gravity.
A spinning top does not stop unless it is resisted by air.
Planets and comets retain their motion as there is less resistance in outer space

Law 2

The change of motion is proportional to the external motive force impressed. It follows the direction of that force.

Corollaries 1-2

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Corollary 1

A body that is moved by two perpendicular forces will move in a diagonal

Corollary 3

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COROLLARY 3

The quantity of motion collected by adding the motions directed towards the same parts, and the difference of those that are directed to contrary parts, suffers no change from the action of bodies among themselves.

Corollaries 4-6

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COROLLARY 4

The common centre of gravity of two or more bodies does not alter its state of motion or rest by the actions of the bodies among themselves; and therefore the common centre of gravity of all bodies acting upon each other (excluding outward actions and impediments) is either at rest, or moves uniformly in a right line.

Scholium

Mon, 01 Jan 0001 00:00:00 +0000

Galileo discovered Law 1, 2, and Corollaries 1, 2 as bodies:

falling in the duplicate ratio of the time [as seconds squared]
moving in a parabola as projectiles

The uniform gravity of a body acts equally in equal particles of time on that body to create equal velocities. In the whole time, gravity impresses a whole force and generates a velocity proportional to that time.

Scholium: Newton's Cradle

Mon, 01 Jan 0001 00:00:00 +0000

Thus, trying the thing with pendulums of 10 feet, in unequal as well as equal bodies, and making the bodies to concur after a descent through large spaces, as of 8, 12, or 16 feet,

Scholium Continued

Mon, 01 Jan 0001 00:00:00 +0000

Suppose an obstacle is interposed to hinder the congress of 2 bodies A, B, mutually attracting each other.