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  1. 1. The Ordered Universe Chapter 2 Great Idea: Newton’s laws of motion and gravity predict the behavior of objects on Earth and in space
  2. 2. Chapter Outline <ul><li>The Night Sky </li></ul><ul><li>The Birth of Modern Astronomy </li></ul><ul><li>The Birth of Mechanics </li></ul><ul><li>Isaac Newton and the Universal Laws of Motion </li></ul><ul><li>Momentum </li></ul><ul><li>The Universal Force of Gravity </li></ul>
  3. 3. The Night Sky
  4. 4. The Night Sky <ul><li>Movement of stars, planets, sun </li></ul><ul><ul><li>Key for survival of ancestors </li></ul></ul><ul><li>Astronomy </li></ul><ul><ul><li>First science </li></ul></ul><ul><li>Ancient observers: </li></ul><ul><ul><li>Physical events are quantifiable and therefore predictable </li></ul></ul>
  5. 5. Stonehenge <ul><li>Started in 2800 B.C. </li></ul><ul><ul><li>Built over long time </li></ul></ul><ul><ul><li>Built by different peoples </li></ul></ul><ul><li>Marks passage of time </li></ul><ul><ul><li>Specifically the seasons </li></ul></ul><ul><li>Still functions today </li></ul>
  6. 6. Stonehenge
  7. 7. Science in the Making <ul><li>The Discovery of the Spread of Disease </li></ul>
  8. 8. Science by the Numbers <ul><li>Ancient Astronauts </li></ul>
  9. 9. The Birth of Modern Astronomy
  10. 10. The Historical Background: Ptolemy <ul><li>Ptolemy </li></ul><ul><ul><li>2nd century A.D. </li></ul></ul><ul><ul><li>First planetary model </li></ul></ul><ul><ul><li>Earth at center, stationary </li></ul></ul><ul><ul><li>Stars and planets revolved around earth </li></ul></ul>
  11. 11. The Historical Background: Ptolemy
  12. 12. The Historical Background: Copernicus <ul><li>Copernicus </li></ul><ul><ul><li>1543: On the Revolutions of the Spheres </li></ul></ul><ul><ul><li>Sun at center </li></ul></ul>
  13. 13. The Historical Background: Copernicus
  14. 14. Observations: Tycho Brahe and Johannes Kepler <ul><li>Tycho </li></ul><ul><ul><li>Observed new star </li></ul></ul><ul><ul><ul><li>Showed heavens can change </li></ul></ul></ul><ul><ul><li>Designed and used new instruments </li></ul></ul><ul><ul><ul><li>Collected data on planetary movement </li></ul></ul></ul><ul><li>Kepler (Tycho’s colleague) </li></ul><ul><ul><li>First Law: </li></ul></ul><ul><ul><ul><li>Planets have elliptical orbits </li></ul></ul></ul>
  15. 15. Kepler’s First Law
  16. 16. The Birth of Mechanics
  17. 17. Galileo Galilei <ul><li>Mechanics: motions of material objects </li></ul><ul><li>Galileo (1564–1642) </li></ul><ul><ul><li>Mathematics professor </li></ul></ul><ul><ul><li>Inventor </li></ul></ul><ul><ul><li>First to record observations with telescope </li></ul></ul><ul><ul><ul><li>Supported Copernicus’ view </li></ul></ul></ul>
  18. 18. Telescopes Used by Galileo Galilei
  19. 19. Science in the Making <ul><li>The Heresy Trial of Galileo </li></ul>
  20. 20. Speed, Velocity, and Acceleration <ul><li>Speed=distance traveled over time </li></ul><ul><li>Velocity=speed with direction </li></ul><ul><li>Equation for speed: </li></ul><ul><li>Acceleration=rate of change of velocity </li></ul><ul><li>Equation for velocity: </li></ul>
  21. 21. The Founder of Experimental Science <ul><li>Galileo </li></ul><ul><ul><li>Relationship among distance, time, velocity and acceleration </li></ul></ul><ul><ul><li>Found objects accelerate while falling </li></ul></ul>
  22. 22. Galileo’s Falling-Ball Apparatus
  23. 23. Galileo cont. <ul><li>Constant acceleration </li></ul><ul><ul><li>Balls on a plane: v=at </li></ul></ul><ul><li>Freefall </li></ul><ul><ul><li>Constant acceleration at g </li></ul></ul><ul><ul><li>g = 9.8 m/s 2 =32 feet/s 2 </li></ul></ul><ul><ul><li>Distance traveled ( d )=½ at 2 </li></ul></ul>
  24. 24. Accelerated Motion of a Falling Apple
  25. 25. Equations Relating d,v,a , and t
  26. 26. The Science of Life <ul><li>Experiencing Extreme Acceleration </li></ul>
  27. 27. Isaac Newton and the Universal Laws of Motion
  28. 28. The First Law <ul><li>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 </li></ul><ul><li>Uniform motion vs. acceleration </li></ul><ul><li>Force </li></ul><ul><li>Inertia </li></ul>
  29. 29. Hammer Thrower
  30. 30. The Second Law <ul><li>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 </li></ul><ul><li>Equation: F=ma </li></ul>
  31. 31. The Third Law <ul><li>Interacting object exert equal but opposite forces upon each other </li></ul><ul><li>The reactions may not be equal and opposite </li></ul>
  32. 32. Newton’s Laws of Motion at Work
  33. 33. Newton’s Laws of Motion at Work
  34. 34. Newton’s Laws at Work
  35. 35. Momentum
  36. 36. Momentum <ul><li>Motion depends on mass and speed </li></ul><ul><li>Linear momentum: </li></ul><ul><ul><li>p=mv </li></ul></ul><ul><li>Law of conservation of linear momentum </li></ul><ul><li>Angular momentum </li></ul>
  37. 37. The Law of Conservation of Linear Momentum
  38. 38. The Conservation of Angular Momentum
  39. 39. The Universal Force of Gravity
  40. 40. The Universal Force of Gravity <ul><li>Gravity </li></ul><ul><li>Newton’s law of universal gravitation </li></ul><ul><ul><li>F = Gm 1 m 2 / d 2 </li></ul></ul>
  41. 41. The Influence of the Force of Gravity
  42. 42. The Gravitational Constant, G <ul><li>G-constant of direct proportionality </li></ul><ul><ul><li>Universal </li></ul></ul><ul><li>Henry Cavendish </li></ul><ul><ul><li>G = 6.67 x 10 –11 m 3 /s 2 -kg or </li></ul></ul><ul><ul><li>6.67 x 10 –11 N-m 2 /kg 2 </li></ul></ul>
  43. 43. The Cavendish Balance
  44. 44. Weight and Gravity <ul><li>Weight </li></ul><ul><ul><li>Gravity acting on an object’s mass </li></ul></ul><ul><li>Weight depends on gravity </li></ul><ul><ul><li>Different on earth vs. moon </li></ul></ul><ul><li>Mass is constant </li></ul>
  45. 45. Big G and Little g <ul><li>Closely related: </li></ul><ul><ul><li>Force = ( G x mass x M E )/ R E 2 </li></ul></ul><ul><ul><li>Force = mass x g </li></ul></ul><ul><li>Setting equations equal: </li></ul><ul><ul><li>Mass x g = ( G x mass x M E )/ R E 2 </li></ul></ul><ul><ul><ul><li>Divide by mass </li></ul></ul></ul><ul><ul><li>g = ( G x M E )/ R E 2 </li></ul></ul><ul><ul><ul><li>Plug in values </li></ul></ul></ul><ul><ul><li>9.8 N-kg = 9.8m/s 2 </li></ul></ul>
  46. 46. Halley’s Comet in 1985