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• Galileo Galilei


  • Italian Scientist who first explained the concept of Inertia
  • His assertion was the inspiration for Newton's 1st Law of Motion
  • They both imply that no force is needed to keep the motion of an object and the object's inertia would keep it from changing its state of motion

  
• Horizontal Motion


  • An object in motion, if unimpeded, will continue to be in motion, and an external force is not necessary to maintain the motion
  • If a ball is pushed on an infinitely flat plane, the ball will continue to roll if unimpeded
• Vertical Motion


  • In the absence of a resistance, objects would fall not depending on their weight, but in the time of fall
  • If the object encounters a resistive force from a fluid equal to or greater than its weight, it will slow down and reach a uniform motion until it reaches the bottom and stops
  • Without any resistance, a 1-kg object will be as fast as a 10-kg object when falling because they fall within the same amount of time, given that they are released from the same height
  • A stone dropped in the ocean will sooner or later travel at constant speed
• Projectile Motion


  • Galileo believed that a projectile is a combination of uniform motion in the horizontal direction and uniformly accelerated motion in the vertical direction
  • If it is not impeded, it will continue to move even without an applied force
  • When you shoot a ball in a basketball ring, the ball does not need a force to keep it moving

  
• Aristotelian View of Motion


  Based on Aristotle's observation, which made his ideas acceptable and stood for many years

  
• Aristotle


  One of the most influential Greek philosophers whose ideas were the basis for many concepts at that time
• Motion


  • An object's change in motion over time
  • According to Aristotle, motion can either be a natural or a violent motion

  
• Vertical Motion (Aristotelian)


  • Referred to as natural motion
  • The object will move and will return to its natural state based on the object's material or composition - earth, water, air, and fire
  • Aristotle believed that because a ball fell when thrown upward, its element was earth
  • Smoke goes up in the air because it seeks its natural space in the atmosphere
  • Aristotelian concept of natural motion is largely vertical motion

  
• Horizontal Motion (Aristotelian)


  • An object moving in a violent motion requires push or pull to maintain horizontal motion
  • Motion continues only so long as there is an applied force to an object
  • When the force is removed, motion stops
  • Violent motion is imposed caused by pushing or pulling
  • Aristotle classified any motion that required a force as a "violent motion"

  
• Projectile Motion (Aristotelian)


  • Aristotle believed that the projectile motion of an object is parallel to the ground until it is the object's time to fall back into the ground
  • An impetus will be kept by the object until such time that the initial force is forgotten, and the object returns to its natural state to stop moving and fall to the ground
  • He viewed projectile motion as natural and violent motion
  • He said that heavy objects fall faster than light ones

  
• Isaac Newton


  • English mathematician and mathematician and physicist who lived from 1642-1727
  • He is also the one who discovered gravity
• Newton's Laws of Motion


  • An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force
  • The acceleration of an object depends on the mass of the object and the amount of force applied
  • Whenever one object exerts a force on another object, the second object exerts an equal and opposite on the first

  
• Newton's First Law: Inertia


  • An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force
  • This tendency to resist changes in a state of motion is inertia
  • If all the external forces cancel each other out, then there is no net force acting on the object
  • If there is no net force acting on the object, then the object will maintain a constant velocity

  
• Examples of inertia involving aerodynamics


  • The motion of an airplane when a pilot changes the throttle setting of an engine
  • The motion of a ball falling down through the atmosphere
  • A model rocket being launched up into the atmosphere
  • The motion of a kite when the wind changes
• Newton's Second Law: Force


  • The time rate of change of the momentum of a body is equal in both magnitude and direction to the force imposed on it
  • The momentum of a body is equal to the product of its mass and its velocity
  • If a body has a net force acting on it, it is accelerated in accordance with the equation F = ma
  • If a body is not accelerated, there is no net force acting on it
• Newton's Third Law: Action & Reaction


  • For every action (force) in nature there is an equal and opposite reaction
  • If object A exerts a force on object B, object B also exerts an equal and opposite force on object A
  • Forces result from interactions
• Why do objects move?
• Aristotle's view on motion


  • Motion can be either natural or violent motion
  • In a natural motion, the object will move and will return to its natural state based on the object's material or composition
  • In contrast, an object moving in a violent motion requires an external force (push or pull) for the object to move

  
• Aristotle's view on projectile motion


  • An object thrown at a certain angle is given an impetus - a force or energy that permits an object to move
  • It will continue to move in such state until the object's impetus is lost, and the object returns to its natural state, causing it to stop and fall to the ground

  
• Galileo's view on motion


  • Motion can be described by mathematics and the changes in some physical variables such as time and distance
  • An object in uniform motion will travel a distance that is proportional to the time it will take to travel
  • A uniformly accelerating object will travel at a speed proportional to some factor of time
  • An object in motion, if unimpeded, will continue to be in motion; an external force is not necessary to maintain the motion

  
• Galileo disproved Aristotle's claims and believed that the motion of objects is not simply due to the composition of objects