Ch02
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Transcript of Ch02
![Page 1: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/1.jpg)
The Ordered Universe
Chapter 2
Great Idea:Newton’s laws of motion and gravity predict the
behavior of objects on Earth and in space
![Page 2: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/2.jpg)
Chapter Outline
• The Night Sky• The Birth of Modern Astronomy• The Birth of Mechanics• Isaac Newton and the Universal Laws
of Motion• Momentum• The Universal Force of Gravity
![Page 3: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/3.jpg)
The Night Sky
![Page 4: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/4.jpg)
The Night Sky
• Movement of stars, planets, sun– Key for survival of ancestors
• Astronomy– First science
• Ancient observers:– Physical events are quantifiable and
therefore predictable
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Stonehenge
• Started in 2800 B.C.– Built over long time– Built by different peoples
• Marks passage of time– Specifically the seasons
• Still functions today
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Stonehenge
![Page 7: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/7.jpg)
Science in the Making
• The Discovery of the Spread of Disease
![Page 8: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/8.jpg)
Science by the Numbers
• Ancient Astronauts
![Page 9: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/9.jpg)
The Birth of Modern Astronomy
![Page 10: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/10.jpg)
The Historical Background: Ptolemy
• Ptolemy• 2nd century A.D.
• First planetary model• Earth at center, stationary• Stars and planets revolved around earth
![Page 11: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/11.jpg)
The Historical Background: Ptolemy
![Page 12: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/12.jpg)
The Historical Background: Copernicus
• Copernicus• 1543: On the Revolutions of the Spheres• Sun at center
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The Historical Background: Copernicus
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Observations: Tycho Brahe and Johannes Kepler
• Tycho– Observed new star
• Showed heavens can change
– Designed and used new instruments• Collected data on planetary movement
• Kepler (Tycho’s colleague)– First Law:
• Planets have elliptical orbits
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Kepler’s First Law
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The Birth of Mechanics
![Page 17: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/17.jpg)
Galileo Galilei
• Mechanics: motions of material objects
• Galileo (1564–1642)– Mathematics professor– Inventor– First to record observations
with telescope• Supported Copernicus’ view
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Telescopes Used by Galileo Galilei
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Science in the Making
The Heresy Trial of Galileo
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Speed, Velocity, and Acceleration
• Speed=distance traveled over time• Velocity=speed with direction
• Equation for speed:
• Acceleration=rate of change of velocity
• Equation for velocity:
t
dv
t
vva if
![Page 21: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/21.jpg)
The Founder of Experimental Science
• Galileo– Relationship among distance, time,
velocity and acceleration– Found objects accelerate while falling
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Galileo’s Falling-Ball Apparatus
![Page 23: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/23.jpg)
Galileo cont.
• Constant acceleration– Balls on a plane: v=at
• Freefall– Constant acceleration at g– g = 9.8 m/s2=32 feet/s2
– Distance traveled (d)=½at2
![Page 24: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/24.jpg)
Accelerated Motion of a Falling Apple
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Equations Relating d,v,a, and t
![Page 26: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/26.jpg)
The Science of Life
• Experiencing Extreme Acceleration
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Isaac Newton and the Universal Laws of Motion
![Page 28: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/28.jpg)
The First Law
• An object will continue moving in a straight line at a constant speed, and a stationary object will remain at rest, unless acted upon by an unbalanced force
• Uniform motion vs. acceleration• Force• Inertia
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Hammer Thrower
![Page 30: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/30.jpg)
The Second Law
• The acceleration produced on a body by a force is proportional to the magnitude of the force and inversely proportional to the mass of the object
• Equation: F=ma
![Page 31: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/31.jpg)
The Third Law
• Interacting object exert equal but opposite forces upon each other
• The reactions may not be equal and opposite
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Newton’s Laws of Motion at Work
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Newton’s Laws of Motion at Work
![Page 34: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/34.jpg)
Newton’s Laws at Work
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Momentum
![Page 36: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/36.jpg)
Momentum
• Motion depends on mass and speed• Linear momentum:
– p=mv
• Law of conservation of linear momentum
• Angular momentum
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The Law of Conservation of Linear Momentum
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The Conservation of Angular Momentum
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The Universal Force of Gravity
![Page 40: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/40.jpg)
The Universal Force of Gravity
• Gravity
• Newton’s law of universal gravitation– F=Gm1m2/d2
![Page 41: Ch02](https://reader038.fdocuments.in/reader038/viewer/2022103013/54663b11af795937498b70a8/html5/thumbnails/41.jpg)
The Influence of theForce of Gravity
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The Gravitational Constant, G
• G-constant of direct proportionality– Universal
• Henry Cavendish– G = 6.67 x 10–11m3/s2-kg or
6.67 x 10–11N-m2/kg2
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The Cavendish Balance
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Weight and Gravity
• Weight– Gravity acting on an object’s mass
• Weight depends on gravity– Different on earth vs. moon
• Mass is constant
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Big G and Little g
• Closely related:– Force = (G x mass x ME)/RE
2
– Force = mass x g• Setting equations equal:
– Mass x g = (G x mass x ME)/RE2
• Divide by mass
– g = (G x ME)/RE2
• Plug in values
– 9.8 N-kg = 9.8m/s2
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Halley’s Comet in 1985