Physical Science

• Motion diagram


  A representation of an object's motion showing its position at different times

  
• Particle model


  A simplified version of a motion diagram in which the object in motion is replaced by a series of single points
• Object in motion


  • Running
  • Walking
  • Shouting
  • Climbing
• Movement travels in many directions such as straight-line, curved, spiral, and back-and-forth
• Straight-line motion


  Motion that follows a path directly between two points without turning left or right
• Displacement


  The change in position of an object, calculated as the difference between the final and initial positions

  
• Graphing motion


  1. Identify final and initial position

  2. Calculate displacement

  3. Calculate time consumed/elapsed

  
• A motion diagram is a series of images showing the positions of a moving object at equal time intervals

  
• The purpose of a motion diagram or particle model is to check whether an object is in motion
• Graphing motion data


  1. Determine initial and final time

  2. Determine initial and final position

  3. Calculate displacement

  4. Describe the object's motion

  
• Kepler's laws describe the motion of planets around the sun
• Kepler's First Law (Law of Ellipses)


  The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus
• Kepler's Second Law (Law of Equal Areas)


  An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time
• Kepler's Third Law (Law of Harmonies)


  The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun
• Tycho Brahe made important contributions by devising the most precise instruments available for observing the heavens
• Foci


  A constant
• Kepler's Second Law (Law of Equal Areas)


  1. An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time

  2. Planets move fastest along their orbital path when they are closest to the Sun
• Radius Vector


  An imaginary line from the sun joining the planet
• Harmonices Mundi (Harmony of the world) - Kepler's Third Law published


  1619
• Tycho Brahe


  • A Danish nobleman, made important contributions by devising the most precise instruments available for observing the heavens before the telescope's invention
  • From Uraniborg, on an island in the south between Denmark and Sweden called Hveen, Brahe made his observations
  • The tools of Brahe enabled him to determine the detailed motions of the planets more precisely than was possible
  • Brahe compiled extensive data on the planet Mars, which would later prove crucial to Kepler, because it would be sufficiently accurate to demonstrate that the orbit of Mars was not a circle, but an ellipse
• Although Copernicus correctly observed that the planets revolve around the Sun, it was Kepler who defined their orbits correctly
• Kepler


  • Became the assistant of a wealthy astronomer at the age of 27, Tycho Brahe, who asked him to define Mars' orbit
  • Kepler, like many philosophers of his era, had a mystical belief that the circle was the perfect form of the Universe, and that the orbits of the planets must be circular as a manifestation of the Divine order
  • He struggled for many years to make Brahe's observations of Mars' motions match a circular orbit
• Nicolaus Copernicus


  • Father of Modern Astronomy
  • A Renaissance polymath, active as a mathematician, astronomer, and Catholic canon, who formulated a model of the universe that placed the Sun rather than Earth at its center
• Aristotle and Galileo were the two of the most important historical figures in physics
• Motion


  The movement or change in location of an object overtime, often described in terms of direction, location and speed
• Aristotle's concepts of motion


  • Celestial motion
  • Natural motion
  • Violent motion
• Celestial motion


  Motion of the sun, moon, and stars in perfect circles, formed of perfect incorruptible substance called ether or quintessence
• Natural motion


  Straight up or straight down, solid objects or liquids fall because they seek their natural resting place which is the center of the earth, air/smoke/flames rise upwards
• Violent motion


  Imposed motion or horizontal motion, the result of forces that pushed or pulled it, had an external cause
• Galileo


  • Argued that an object can move freely in the absence of friction, thus only when friction is present, a force is needed to keep an object moving
  • Outspoken in his support of Copernicus who proposed that the earth is continuously moving around the sun
  • One of galileo's great contributions to physics was demolishing the notion that a force is necessary to keep an object moving
• Friction


  The force that acts between materials that touch as they move past each other, caused by the irregularities in the surfaces of objects that are touching
• If friction were entirely absent a ball moving horizontally would move forever, no push or pull would be required to keep it moving once it is set in motion
• Inertia


  The tendency of an object to resist being moved, or if the object is moving, to resist a change in direction until an outside force acts on the object
• A ball is rolled across a countertop and rolls slowly to a stop


  According to Aristotle, the ball stops because it seeks its natural state of rest

  According to Galileo, the friction between the ball and the table overcome the ball's natural tendency to continue rolling – overcomes the ball's inertia – and brings it to stop
• Freefall - of motion where no other external forces aside from gravity influences the acceleration of an object


  According to Aristotle, if you drop a piece of paper and a coin from the same height at the same time, the coin would fall faster and hit the ground first because it is heavier

  According to Galileo, he wanted to prove the rate of fall or acceleration of an object is independent of their mass
• In 1971, the famous astronaut David Scott proved Galileo correct in his famous hammer/feather experiment on the moon, during the Apollo 15 mission
• Since there is no air in the moon, the objects dropped at the same speed
• In the year Galileo died, Isaac Newton (1642-1727) was born, and by the age of 23 Newton gave the world his famous three laws of motion
• Together, Galileo and Newton discredited the Aristotelian of motion and developed the theories that still form the basis of Mechanics today
• Astronomers claim that earth is much like a spherical ball