Transcript Chapters Two and Three

Chapter Two and
Chapter Three
Objectives
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What is Motion?
Measuring Motion
Artstotle’s views
Horizontal versus Vertical Motion
Newton’s Laws of Motion
Momentum
Circular Motion
Law of Gravition
Motion and Measuring Motion
 Change in position
 Passage of time
 Measuring Motion
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Speed
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Distance/time
Instantaneous versus Average
Velocity
Acceleration
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Change of velocity/ time
Acceleration versus Deacceleration
Motion Examples
 Speed: Example 2.1
 Acceleration: Example 2.3
Aristotle’s Views
 Two spheres
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Sphere of perfection versus Sphere of change
 Natural versus Forced Motion
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Elements: earth, air, fire, and water
Reqired force by people
 Could not explain interaction at a distance
Horizontal versus Vertical
Motion
 Horizontal
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Leaning Tower of Pisa
Rolling Balls
Inertia
 Vertical
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Free fall
Galileo versus Aristotle
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Constant versus Accelerating objects
Horizontal versus Vertical
(cont.)
 Vertical (cont.)
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D=(1/2)at2
Confirmed with rolling ball
A=g=9.8 m/s2
T=(2d/g)
 Compound Motion
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A combination of vertical and horizontal motion
Newton’s Laws of Motion
 Edmund Halley
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Christmas Day, 1642
Trinity College, Cambridge
Halley: Principia, planetary motion
Well accepted
Newton’s First Law of Motion
 “Every object retains it state of motion of its
stat of uniform straight-line motion unless
acted up by an unbalanced force”
 Inertia
 Mass
Newton’s Second Law of
Motion
 “The acceleration of an object is directly
proportional to the net force acting on it and
inversely proportional to the mass of the
object”
 Weight is a force
 F = ma
Newton’s Third Law of Motion
 “Whenever two objects interact, the force
exerted on one object is equal in size and
opposite in direction to the force exerted on
the other object”
 Example: Standing on the Floor
 FAB = FBA
Newton Examples
 Second Law: Example 3.1
 Third Law: Example 3.5
Momentum
 “The total momentum of a group of
interacting objects remains the same in the
absence of external forces”
 P=mv
 Unusual
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P gives no clues
Kg m/s has no other name
Circular Motion
 Centripetal versus Centrifugal
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No true Centrifugal
 All circular motion inside
 ac=v2/r
 F=mv2/r
Newton’s Laws of Gravitation
 “Every object in the universe is attractedto
every other object with a force that is directly
proportional to the product of their masses”
 F = GM1M2/R2
 G = 6.67 X 10-11 Nm2/kg2
Force and Gravitation Examples
 Circular Motion: Example 3.7
 Gaviation: Example 3.9, 3.10
Homework
 Chapter Two
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Questions for Thought
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1, 6, 9
Parallel Exercise
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3, 5
 Chapter Three
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Questions for Thought
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1, 4, 9
Parallel Exercise
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4, 10