physci part 2

• Theorists


  Someone who considers given facts & comes up with a possible explanation
• Theorists

  • Geocentric Theorists
  • Heliocentric Theorists
• Pythagoras


  • He was the first one to originate a spherical earth using observations such as North & South Constellations, Sinking Ships, Lunar Eclipse

  
• Geocentric Theorists


  Earth at the center of the solar system, Sun & other planets orbiting around it

  
• Geocentric Theorists

  • Plato
  • Aristotle
  • Ptolemy
  • Tycho Brahe
• Plato

  • The earth is a form of a globe having its extremes in every direction equally distant from the center, The planet is at the center of universe, perfect & eternal, has four elements (Fire, Earth, Air, Water)

  
• Aristotle


  • His work on 350 BC entitled, "On the Heavens" initiated the idea of a geocentric universe with fixed spherical earth at its center, Three arguments (Rounded shadow which the earth projects on the moon, Change in the constellations as travelers voyage to southern & northern regions, Indirect idea on gravity)

  
• Eratosthenes


  • Ancient scholar tried to provide proof of a spherical Earth & its circumference through calculations, It was Eratosthenes who gave the most accurate size during their time through non-scientific calculations
• Heliocentric Theorists


  The solar system places the sun at the center, Planets orbiting around it

  
• Heliocentric Theorists

  • Aristarchus of Samos
  • Nicolaus Copernicus
  • Galileo Galilei
  • Johannes Kepler
• Astronomy


  Study of everything in the universe beyond Earth's atmosphere, Objects we can see with our naked eyes (Sun, Moon, Planets, Stars)
• Cosmology


  Study the origin & evolution of the universe
• Plato


  • He believed that the universe is perfect/ethereal & unchanging, He further described the stars embedded in the outer space as eternal & divine, "What uniform & ordered circular motion must be assumed for each of the planets to account for their apparently irregular annual paths?"

  
• Eudoxus of Cnidus


  • There are 27 interconnected geocentric spheres
• Claudius Ptolemy


  • Earth is spherical object, The stars are fixed bodies attached to a solid spherical exterior part of the universe, Planets moved independently of the fixed stars, Sometimes, the planet seem to reverse their motion

  
• Aristarchus of Samos


  • Stated that sun & stars are fixed, Estimated the sizes of the Sun & Moon as compared to Earth's size (Moon's diameter was 0.32-0.40x the diameter of Earth, Sun's diameter was 6.3-7.2x the diameter of Earth), Estimated the distance from the Earth to the Sun & Moon (Sun is about 18-20x farther away from the Earth than Moon)

  
• Modern Astronomy


  • Observations became more quantitative in nature, Theories formulated are based on logical & mathematical concepts
• Nicolaus Copernicus


  • Corrected the Geocentric theory & proposed the Heliocentric theory with postulates (Earth is considered as only one of the planets, Earth rotates on its axis daily & revolves around the sun once a year, Earth experiences an annual tilting of its axis, The retrograde motion of the planets is explained by earth's motion, Distance from earth to sun is small compared to earth's distance from the stars, Tilting of the Earth & the four seasons)

  
• Tycho Brahe


  • Modified the geocentric model of the universe, Designed & built huge instrument used to make precise measurements of the positions of the planets, Discovered the supernova in the constellation Cassiopeia in 1572, Made observations of planetary motions that are important to the development of Kepler's Laws & other models of solar system, Tychonic System

  
• Galileo Galilei


  • Observed sunspots & rough surface of the moon, Discovered the 4 famous moons of Jupiter known as Galilean moons (Io, Europa, Ganymede, Callisto), Discovered that Venus has phases like moon

  
• Johannes Kepler


  • First Law: States that the orbits of the planets are ellipses, with the sun at one focus, Second Law: States that an imaginary line drawn from the sun to a planet sweeps out equal areas in equal intervals (Perihelion - Nearest to the sun, Aphelion - Farthest from the sun), Third Law: The cube of the radius of the orbit of a planet around the sun is proportional to the square of its period of revolution

  
• Aristotle's Theory of Motion


  • Stated that all objects on Earth were believed to be a mixture of four primordial elements: Fire, Earth, Air, Water
  • Concept of chemical change can be applied
  • He proposed that the motion is of two types: Natural and Violent
• Longevity of Aristotle's Theory of Motion


  • The theory was consistent with common sense
  • No other theories about motion were available during Aristotle's time
  • The quantitative method of observation to prove the validity was not yet developed
  • No equipment available, just common sense
• Natural Motion


  It exists as any type of motion that a body does naturally, without forcing the motion to happen
• Four Theories of Natural Motion


  • An object which is made up of an "Earth" material falls toward the center of Earth because it seeks its natural place
  • Heavy objects fall faster than the lighter ones
  • Objects fall faster in air than in water because of the difference in density
  • Objects sometimes move away from their natural places, e.g. Leaves (decomposition)
• Violent Motion


  Exists when a motion requires a force to make an object move in "unnatural" manner
• Galileo's Findings about Motion


  • Two objects (light & heavy) dropped simultaneously from the tower of Pisa, fell & struck the earth at the same time, proving acceleration due to gravity
  • A marble made to roll on flat surface would roll for an infinite amount of time, proving the Law of Inertia
  • The ratio of the distance (d) covered & the square of the corresponding time (t) was constant when a marble was rolled down on an inclined plane at a fixed angle, proving Velocity
  • The gravitational force of the earth on a freely falling object causes the object to be a uniformly accelerated as it goes toward the surface of the earth, proving Uniformly Accelerated Motion
• Free Fall Motion


  A type of motion under the sole influence of gravity, downward motion
• Vertical Upward Motion


  Follows a motion resisting the effect of acceleration due to gravity

  
• Projectile Motion: 2D


  • Combines velocity (x) & acceleration (y)
  • Upward motion is independent in gravity
  • Downward motion is independent in gravity
  • Projectile Motion is the motion of an object thrown
  • Trajectory is the path