SCI 8, Q1, Advance Study

• Inertia


  • Moving objects don't spontaneously speed up, slow down, or change direction
  • You have to overcome inertia to get an object moving
  • An object stays still unless someone/something moves it
  • Objects remain still or in motion unless a force acts upon it
• Force


  • Product of Mass x Acceleration
  • Allow you to overcome inertia
  • Must be applied to cause an object accelerate or speed up
  • The more force you applied, the quicker you accelerate
  • The heavier an object, the more force it needs to move or accelerate
• Action-Reaction Pair


  • For every action, there is an opposite reaction
  • If you exert force on an object, it causes a reaction of equal & opposite force
• Displacement


  The gap between the initial position & the final position of an object
• Velocity


  The speed at which something moves in one direction
• Acceleration


  The time rate of change of the velocity of an object
• Force


  • Push & pull applied to an object
  • An influence that changes the motion of an object
  • The primary cause of all the motion & movements we see every day
  • Force is present even if an object isn't moving
• Magnitude


  • Refers to how strong the force is
  • Is expressed in various ways
• Newton


  • Meter-Kilogram-Seconds System (MKS)
  • The international system of units is commonly expressed in Newtons
  • Named after a famous physicist & mathematician named Sir Isaac Newton
• Dyne (dyn)


  Centimeter-Gram-Second (CGS)
• Pound (lbs)


  Foot-Pound-Second System (FPS)
• Direction


  Refers to the points to where the object goes
• Point of Application


  Location where the force is applied
• Line of Action


  • Straight line passing through the point of application
  • Is parallel to the direction of the force
• Types of Force


  • Contact Forces
  • Non-Contact Forces
• Contact Forces


  Forces wherein an object needs a physical contact to another object
• Applied Force


  The force exerted by someone or something towards another person or object
• Friction Force


  • The force that acts opposite or against another object
  • Slows down the movement of someone or something
• Normal Force


  • The force that acts perpendicular to an object
  • Supports an object as surface resists compression
• Tension Force


  • The force applied to a string, rope, chain, cable, & the like
  • A force countering the stretching force applied
  • Resists force that causes object to stretch
• Non-Contact Forces


  Forces where objects do not touch or aren't in contact w/ each other
• Gravitational Force


  • The force that attracts objects towards the Earth
  • The greater the mass, the greater the gravitational force that pulls it down
• Magnetic Force


  • The force that is exerted on what we call a field of attraction or repulsion
  • When using a magnet, attraction occurs only between opposite poles
• Balanced Forces


  • Are those which are of opposite directions & equal in magnitude
  • Makes an object at rest (no motion)
• Unbalanced Forces


  Are those which are in opposite direction & unequal in magnitude (There's a motion)
• Net Force/Resultant Force


  • The sum of the existing forces that acts on an object
  • If the net force is 0, the forces are balanced/no movement or change in velocity (0 = balanced)
  • If the net force is greater than 0, that means that there's a greater amount of force, so expect a change in motion & velocity of an object
• How to solve Net Force

  1. Use the formula: Sigma F = ma

  2. Use algebraic signs positive & negative to indicate direction of force

  3. Forces exerted to the right get the positive sign

  4. Forces exerted to the left get the negative sign

  5. Forces exerted upwards get a positive sign

  6. Forces exerted downwards get a negative sign
• Motion


  • An object's change in position upon application of force by another object
  • If there's an unbalanced force, it is expected that the object that the force has acted upon will be in motion
• Timeline of the Significant Development of the Concepts of Force & Motion

  • Aristotle
  • John Philoponus
  • Jean Buridan
  • Galileo Galilei
  • Sir Isaac Newton
• Aristotle


  • Believed that a moving object needs continuous application of force to keep it moving
  • To him, an object is naturally at rest
  • The greater the force of an object, the greater is its speed
  • He introduced the idea of impetus
• Impetus


  Keeps a body in motion
• John Philoponus


  • Conceptualized the idea of surrounding force similar to inertia found in Galileo's idea & Newton's first law of motion
  • He first introduced the Theory of Impetus
• Theory of Impetus


  • A concept similar to force
  • According to the theory, when Impetus decreases, the speed of the object also decreases
  • When that Impetus is removed, the object stops moving
• Jean Buridan


  • Also saw Impetus as the cause of movement
  • He further developed the theory of Impetus introduced by Philoponus
  • According to him, motion is possible through a mover that keeps the object moving with power proportional to the speed & mass of the object
  • When the mover is removed, the object stops moving
  • He later named Impetus as Force
• Galileo Galilei


  • Disagreed with Aristotle's claim
  • He claimed that even without a continuous force, an object can continue moving with a constant speed through a straight line if there are no outside forces acting on it
  • He was the first to suggest that uniform speed straight line motion was just as natural as at rest state of motion
  • He called this tendency of an object to maintain its initial state of motion as Inertia
• Galilei's Experiment


  1. He let a perfectly round ball roll down an inclined surface & prepared 3 set-ups under ideal conditions (no friction & air resistance)

  2. 1st set-up: The ball speeds up when released, and slows down when rolling up another inclined surface of the same slope, reaching the same height

  3. 2nd set-up: The ball speeds up when released, and slows down when rolling up another inclined surface that isn't as steep, reaching a further distance

  4. Last set-up: The ball continues to roll in a flat surface, not speeding up nor slowing down
• Galilei concluded that in the absence of friction & air resistance, the ball would continue rolling up to a height above the base equal to the height from where it was released, and on a flat surface, the ball would continue to move forever since there'll be no force to cause its state of motion to change
• Sir Isaac Newton


  • Used Galileo's ideas & eventually formulated the Three Laws of Motion
  • An English Mathematician & Physicist
  • Born on Jan. 4, 1943 in the U.K.
  • One of the most popular & influential scientist in the world
  • Notable for his works & discoveries such as the Laws of Motion
• Science


  • A systematized body of knowledge
  • It is based on facts & is acquired through careful experimentation & observation
  • Many phenomena including force in motion can be explained by actual observation & simple common sense
• Newton's 3 Laws of Motion

  • Law of Inertia
  • Law of Acceleration
  • Law of Interaction