Physical Science

• Motion

  Change in position with respect to time
• Force


  A push or pull that is acting on an object
• Projectile Motion


  A type of motion that involves an object (Called Projectile) being thrown or fired near Earth's surface
• Aristotle considered some of the first ideas about the causes of motion back in the fourth century B.C.
• It was believed by people that Aristotle's motions are true
• Galileo published a book called Two New Science in 1638 about his findings in motion
• It took about thousand years before people began correctly understanding motion
• Horizontal Motion


  • Aristotle associated force with motion, but believed continuous force was necessary for an object to keep moving horizontally
  • Galileo's later findings contradicted Aristotle's view, suggesting that objects in constant horizontal motion require no force unless opposed by friction
  • Galileo's experiments with marbles demonstrated that in the absence of friction, objects maintain constant velocity indefinitely
  • Friction was identified as the primary force opposing motion, with objects continuing in motion unless acted upon by an unbalanced force
• Vertical Motion


  • Aristotle initially proposed that objects fall at a uniform speed proportional to their weight
  • Galileo challenged this by dropping a solid iron ball and a wooden ball simultaneously, demonstrating they hit the ground at the same time, regardless of weight
  • The observation of heavier twigs falling faster than lighter leaves in daily life is explained by air resistance
  • Galileo proposed that without air resistance, objects of different weights fall simultaneously, termed "free fall"
  • The invention of the air pump allowed for the creation of vacuum spaces, where objects like coins and feathers fall together
  • Galileo observed that in free fall, the velocity of an object increased over time, introducing the concept of acceleration
  • He calculated that the distance fallen by a freely falling object is proportional to the square of the time of fall (d ∝ t^2), verified through experiments with rolling balls on inclined boards
• Projectile Motion


  • Aristotle defined projectiles as thrown objects, explaining their motion through the concept of antiperistasis
  • Antiperistasis suggests that a projectile maintains motion through contact with a medium, such as air, which fills the space left behind, providing necessary push
  • John Philoponus argued against Aristotle, stating that the medium resists motion, with motive force retained within the object itself
  • Jean Buridan expanded on Philoponus's idea, introducing the concept of impetus, which is the impressed force in a projectile causing continued motion
  • Galileo observed that projectiles follow a curved path due to the combination of vertical (gravity) and horizontal motion
  • He identified the curve as a parabola, realizing that the horizontal motion is uniform and constant due to the principle of inertia
  • Aristotle's ideas were based on observation and thought, lacking experimental verification, while Galileo's were experimentally validated and mathematically verified
• The early Greeks had a geocentric view of the earth
• Geocentric view


  Earth is the center hence a motionless sphere
• Greeks also believed that stars travelled daily around the earth but stayed at in a transparent hollow sphere called celestial sphere
• Phythagoras around 500 BC started the idea of spherical earth
• Aristotle provided arguments that support the idea of a spherical Earth
• Aristotle's arguments for a spherical Earth

  • The sphere is a perfect solid and the heavens are regions of perfectness
  • The Earth's component parts, failing naturally towards the center, would press into a round foam
  • In Eclipse of the Moon, the Earth's shadow is always circular; a flat disc would cast an oval shadow
  • Even short travels northward, the Pole Star is higher in the sky
• Greek Philosophers and Mathematician Pythagoras are credited to be the ones that propose a spherical Earth
• Aristotle was the one who gave scientific evidence to proving a spherical Earth
• Aristotle's book "On the heavens" contained evidences proving spherical Earth
• Evidences for a spherical Earth in Aristotle's "On the heavens"


  • During a lunar eclipse, the shadow of the Earth can be seen on the moon. And since the shadow is always round regardless on where the Earth is in its rotation, this proves that the Earth is round
  • The stars are in different positions depending on where you are on Earth. Aristotle stated that this proves that the Earth is not only circular in shape,but it's also a sphere, otherwise a slight change of where you are will not be so quickly apparent
• The Greek knew why Earth is a Sphere because the shape of the Earth's shadow during Lunar eclipse is round. Thus, the shape of the earth is round too, aside from that , travel in latitude changes the position of the star and only spherical shape would allow motion to the center to be straight down
• Anaxagoras


  Able to explain what causes the phases of the moon. According to him, the moon shone only by reflected sunlight. Since it is a sphere, only half of it is lluminated at a time. This illuminated part that is visible from the earth changes periodically
• Eudoxus


  Proposed a system of fixed spheres. He believed that the Sun, the moon, the five known planets and the stars were attached to these spheres which carried the heavenly bodies while they revolved around the stationary Earth
• Aristotle


  Believed that the earth is spherical in shape since it always casts a curved shadow when it eclipses the moon. He also believed that the earth was the center of the universe. The planets and stars were concentric, crystalline spheres centered on the earth
• Aristarchus


  The very first Greek to profess the heliocentric view. The word helios means sun; centric means centered. This heliocentric view considered the sun as the center of the universe. He learned that the sun was many time farther than the moon and that it was much larger than the earth. He also made an attempt to calculate the distance of the sun and the moon by using geometric principles
• Eratosthenes


  The first successful attempt to determine the size of the earth was made by him. He did this by applying geometric principles. He observed the angles of the noonday sun in two Egyptian cities that were almost opposite each other- Syene (now Aswan) in the south and Alexandria in the north. He assumed they were in the same longitude
• Hipparehus


  Considered as the greatest of the early Greek astronomers. He observed and compared the brightness of 850 stars and arranged them into order of brightness or magnitude. He developed a method for predicting the times of lunar eclipses within a few hours. Aside from this, he also measured the length of the year within minutes of the modern value
• Claudius Ptolemy


  Believed that the earth was the center of the universe. His Ptolemic Model claimed that the planets moved in a complicated system of circles. This geocentric model also became known as the Ptolemic System
• Newton pioneered work on the motion of point objects and extended concepts to objects beyond Earth
• Newton compiled his thoughts on motion in his book "Principia" in 1687
• Newton is regarded as one of the greatest physicists
• Newton's Three Laws of Motion

  • Law of Inertia: An object at rest tends to stay at rest, and an object in motion tends to stay in motion with constant velocity unless acted upon by an unbalanced force. Total force applied to an object determines whether the forces are balanced or unbalanced
  • Law of Acceleration: Acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Describes the relationship between force, mass, and acceleration
  • Law of Interaction: For every action, there is an equal and opposite reaction. Action and reaction forces act on different bodies but in opposite directions
• Applications of Newton's Laws

  • Law of Inertia: Headrests in cars prevent neck injuries during collisions, Airbags and seat belts prevent passengers from hitting the dashboard, Coin falls directly into a glass when cardboard is flicked due to inertia
  • Law of Acceleration: Friction cancels out applied force until it surpasses a certain threshold, causing motion. Objects with larger mass have greater inertia and resist changes in motion more
  • Law of Interaction: Fireman holds onto a hose tightly to counteract the force of water surging out, Birds fly by pushing air downward, and the air pushes back, keeping them airborne, Earth is pulled upward by an object in free fall, although this motion is not readily observable due to Earth's significantly larger mass
• Waves


  A periodic disturbance that moves away from a source and carries energy with it
• Waves do not transmit matter but they transmit energy
• Waving your hand causes vibration. Vibration causes motion due to the compression and rarefaction of molecules in a medium. When you observe a wave, t
• Airbags and seat belts


  • Prevent passengers from hitting the dashboard
• Coin falls directly into a glass


  When cardboard is flicked due to inertia
• Friction


  Cancels out applied force until it surpasses a certain threshold, causing motion
• Objects with larger mass


  • Have greater inertia and resist changes in motion more