Chapter Two and Chapter Three

Objectives  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 Speed Distance/time Instantaneous versus Average Velocity Acceleration Change of velocity/ time Acceleration versus Deacceleration

Motion Examples  Speed: Example 2.1  Acceleration: Example 2.3

Aristotle’s Views  Two spheres Sphere of perfection versus Sphere of change  Natural versus Forced Motion Elements: earth, air, fire, and water Reqired force by people  Could not explain interaction at a distance

Horizontal versus Vertical Motion  Horizontal Leaning Tower of Pisa Rolling Balls Inertia  Vertical Free fall Galileo versus Aristotle Constant versus Accelerating objects

Horizontal versus Vertical (cont.)  Vertical (cont.) D=(1/2)at 2 Confirmed with rolling ball A=g=9.8 m/s 2 T=  (2d/g)  Compound Motion A combination of vertical and horizontal motion

Newton’s Laws of Motion  Edmund Halley 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  F AB = F BA

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 P gives no clues Kg m/s has no other name

Circular Motion  Centripetal versus Centrifugal No true Centrifugal  All circular motion inside  a c =v 2 /r  F=mv 2 /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 = GM 1 M 2 /R 2  G = 6.67 X Nm 2 /kg 2

Force and Gravitation Examples  Circular Motion: Example 3.7  Gaviation: Example 3.9, 3.10

Homework  Chapter Two Questions for Thought 1, 6, 9 Parallel Exercise 3, 5  Chapter Three Questions for Thought 1, 4, 9 Parallel Exercise 4, 10