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Chapter 2, 4 &5

Chapter 2, 4 &5. Newton’s Laws of Motion. Aristotle (384-322)BC. Aristotelian School of Thought. Natural Motion. Every Object in the universe has a proper place, determined by its nature. Heavier objects strive harder to be in their proper place.

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Chapter 2, 4 &5

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  1. Chapter 2, 4 &5 Newton’s Laws of Motion

  2. Aristotle (384-322)BC

  3. Aristotelian School of Thought Natural Motion Every Object in the universe has a proper place, determined by its nature. Heavier objects strive harder to be in their proper place. This implies that heavier objects fall faster than lighter objects.

  4. Violent Motion: All motion results from a push or pull. Except for celestial objects (the realm of the Gods), the normal “natural” state of an object was to be at rest. The Earth does not move. Aristotle’s school of thought dominated western culture for the next 2000 years, until the 16th century.

  5. Celestial Spheres

  6. Copernicus and the Moving Earth

  7. Ptolemaic Model

  8. Copernican Model

  9. Copernicus asserts that the Sun is at the center of the solar system instead of the Earth. This runs contrary to the Aristotelian school of thought. 1543 – Copernicus publishes De Revolutionibus

  10. Galileo Galilei

  11. Galileo is considered to be the father of experimental science. Galileo demolished the Aristotelian model by doing experiments and proving it wrong. Inclined plane demo

  12. Galileo’s Inclined Planes Inertia The tendency of a body to resist changes in its motion. Mass is a measure of inertia – A more massive body has more inertia.

  13. Chapter 3 Linear Motion

  14. Description of Motion -Kinematics Average Speed = total distance/time Total distance = (Average speed) x (time)

  15. Velocity Speed in a particular direction Examples 70mi/h due north --- is a velocity 70mi/h ----- is a speed

  16. Approximate Speeds in Different Units 20km/h 12 mi/h 6 m/s 40 km/h 25 mi/h 11 m/s 60 km/h 37 mi/h 17 m/s 65 km/h 40 mi/h 18 m/s 80 km/h 50 mi/h 22 m/s 88 km/h 55 mi/h 24 m/s 100 km/h 62 mi/h 28 m/s 120 km/h 75 mi/h 33 m/s

  17. Velocity is proportional to the time

  18. Acceleration Acceleration = change in velocity/change in time How quickly how fast changes

  19. Constant Acceleration – Free Fall Near the surface of the earth, all objects fall with the same acceleration baring effects from air friction. In this case, a = g = 9.8m/s/s or 32 ft/s/s or a = g = 9.8m/s2 or 32 ft/s2

  20. Distance traveled Assume a= 2 m/s/s and is constant. 4m 1m 9m 1 sec 2 sec 3 sec

  21. The distance traveled is proportional to the time squared.

  22. Distance vs time d = ½ gt2

  23. If a is constant

  24. If the particle starts with an initial velocity of Vo at zero seconds (to = 0 sec) then:

  25. t(sec) V(m/s) Assume Vo = 1m/s and a = 10m/s2

  26. For free-fall

  27. Newton’s Laws of Motion

  28. Newton’s First Law of Motion Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it.

  29. Newton’s Second law of Motion The acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object.

  30. Newton’s Third Law of Motion For every action, there is always opposed an equal reaction. By “action”, we mean a force. Action/reaction forces do not act on the same object.

  31. Types of Forces Gravitational Forces between masses Friction Contact force Normal Contact force Electromagnetic Forces between charges. Forces between nuclear particles (protons, neutron) Nuclear Spring Restoring Forces

  32. When the acceleration is g we have Free Fall m 2m F 2F

  33. When acceleration is zero - Equilibrium N mg

  34. When acceleration is zero - Equilibrium N v = constant f Fa mg

  35. Action/Reaction pairs Action: Tire Pushes on Road Reaction: Road pushes on Tire

  36. Action/Reaction Action: Rocket pushes on gas Reaction: Gas pushes on rocket

  37. Nonlinear Motion Velocity : A vector quantity A B A+B

  38. Vector quantities have magnitude and direction A + B B A R is called the resultant vector R = A + B

  39. The Pythagorean Theorem R2 = A2 + B2 R = A + B A B

  40. Projectile Motion Any object that is projected by some means and continues in motion under the influence of gravity and air resistance is called a projectile. The path of a projectile is called the trajectory

  41. Projectile Motion -g vector

  42. Projectile Range At 30 degrees At 15 degrees

  43. Fast Moving Projectiles Satellites The Earth’s curvature drops a vertical distance of 5 meters every 8,000 meters horizontally

  44. Circular Motion V = r   r

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