# Jan_31 - Gravity and the Expanding Universe Thursday...

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Gravity and the Expanding Universe Thursday, January 31

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Isaac Newton (1642-1727) Discovered 3 Laws of Laws of Motion, Law of Motion, Law of Gravity Gravity
Newton’s First First Law of Motion: An object remains at rest, or moves in a straight line at constant speed, unless acted on by an outside force. Mathematical laws require precise definitions of terms.

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SPEED SPEED = rate at which an object changes its position. VELOCITY VELOCITY = speed plus direction of travel Example: 65 miles per hour. Example: 65 miles per hour to the north.
ACCELERATION ACCELERATION = rate at which an object changes its velocity velocity . Acceleration can involve: 1) increase in speed 2) decrease in speed 3) change in direction.

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Example of acceleration: an apple falls from a tree. Acceleration = 9.8 meters/second/second. After 1 sec, speed = 9.8 meters/sec, After 2 sec, speed = 19.6 meters/sec, etc…
FORCE FORCE = a push or pull acting to accelerate an object. Examples: Gravity = pull Electrostatic attraction = pull Electrostatic repulsion = push

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Restatement of First Law: In the absence of outside forces, velocity is constant constant . after one second after two seconds after three seconds
Second Law of Motion: The acceleration of an object is directly proportional to the force acting on it, and inversely proportional to its mass.

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