PHYSCI Pointers to review

• ANAXAGORAS - proved the Earths spherical shape; during lunar eclipse, the spherical shadow casted on the moon suggested that the Earth's spherical.
• ARISTOTLE - the reason why ship’s hull disappears first than its sail because of the spherical shape of the Earth.
• ERATOSTHENES - successfully calculated the circumference of the Earth through a shadow cast from a stick.
• EXAMPLES OF ASTRONOMICAL EVENTS THAT CAN BE SEEN WITHOUT THE ADVENT OF TELESCOPES

  • Solar and Lunar Eclipses
  • 2. Auroras
  • 3. Constellations
  • 4. Meteor showers
  • 5. Comets
  • 6. Planetary conjunctions
• PROOF THAT THE EARTH IS SPHERICAL

  The appearance of Polaris in the Northern hemisphere all throughout the year.
• PROOF THAT THE EARTH IS SPHERICAL

  The shadow casted from sundial or “Gnomon” of the Babylonian and Egyptians.
• PROOF THAT THE EARTH IS SPHERICAL

  The eclipses and phases of the moon

  The spherical shape of five known planets during the ancient times

  The Earth’s circumference

  Diurnal and annual motion of the star
• Diurnal motion -Describes the apparent daily motion of stars due to Earth’s rotation. Example: sun rises at east and sets in west
• Annual motion – yearly motion of stars due to Earth’s revolution.
• Geocentric model -

  • Earth is at the center of the universe
  • Proposed by Plato
  • Proponents are Plato, Aristotle & Ptolemy
• Plato - Celestial objects are embedded in a crystalline sphere.
• Aristotle - – called it as Aristotelian Universe; suggested that Earth’s location at the center and its spherical shape embodies the concept of perfection.
• Ptolemy - noted that the Earth is a bit off-center that accounts to the unequal motion of celestial objects around it; Ptolemaic System
• Heliocentric model - Sun is at the center of universe
• Aristarchus - proposed the Heliocentric model.
• Aristarchus - He proved that Earth is not fixed and noted that Earth rotates on its axis and causes the diurnal motion of celestial objects.
• Nicolaus Copernicus -suffered the same fate as Aristarchus; called the model as Copernican System
• Johannes Kepler - explains the motion of celestial objects around the sun through the concept of Laws of Planetary Motion.
• Law of Ellipses - paths of the planets around the sun are not a perfect circle.
• Law of Equal Areas - – planets travel more rapidly when they are near the sun than when they are away from it.
• Perihelion - planet is nearest to the sun.
• Aphelion - planet is at its maximum distance from the sun; away from the sun.
• Law of Harmony/ Law of Period -

  • that the square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit”
  • computation of the planets orbital period (in years) and its distance from the sun – semi major axis
• Motion - as the change in position of a moving object from its initial position to its final position, with respect to time.
• Aristotle - every object in the universe has a proper place, determined by its nature.
• Aristotle - Object made of earth will go back to earth, object made of air will rise and go back to the atmosphere.
• Three types of MOTION

  • Celestial
  • Natural
  • Violent
• Celestial - type of motion governing the movement of celestial bodies, in which they revolve around a perfect circle and created from incorruptible substance called “Aether”, the object of perfection.
• Natural - is the motion of an object based on their pre- determined component. It could be straight- up or straight- down (vertical motion) Examples: - Meteorite falling into the ground. -A smoke moving upward into the sky
• Violent -type of motion resulted from pushing or pulling forces that causes an object to move against it will. It could be vertical or horizontal.
• According to Aristotle in Vertical motion: “Heavier object will move and go back to the ground faster while lighter object will stay in the air and moves slowly due to the difference on their natural component.”
• According to Galileo Galilei in Vertical motion: “In the absence of water and air resistance, objects of various weights, when released on the same height at the same time, will fall and hit the ground at the same time.”
• According to Aristotle in Horizontal Motion: “Force, a push or a pull, is necessary in order to move an object along a straight line. If there is no force, the object will stop”.
• According to Galileo Galilei in Horizontal Motion: “In the absence of friction, object will move forever. No push or pull, or even force is necessary to induce a movement on that object once it is already set in motion.”
• According to Aristotle in Projectile Motion: “Object thrown at an angle has a violent and natural motion in it. Once the violent motion stops, natural motion will take its place.”
• According to Galileo Galilei in Projectile Motion: “Object thrown at an angle has a uniform or constant motion in the horizontal direction and a uniformly accelerated motion in the vertical direction,
• Galileo and Newtons concept on Inertia

  GALILEO- INERTIA is the tendency of a moving object to resist change in its current motion.
• Galileo and Newtons concept on Inertia

  NEWTON- INERTIA is the tendency of an object to resist change in its current state, whether at rest or in motion.
• Newton’s Three Laws of Motion

  • Law of Inertia: “A body at rest will remain at rest, and a body in motion will remain in motion unless acted upon by an external force”.
  • Law of Acceleration: “Acceleration of an object has a directly proportional relationship with force and inversely proportional to the mass”.
  • Law of Interaction: states that “For every action, there is an equal and opposite reaction.”
• Acceleration - is the change in velocity over time; increasing velocity.

  Deceleration - decreasing velocity.