module 4

• Aristotelian concepts

  Aristotle's views on vertical motion, horizontal motion, and projectile motion
• Galilean concepts

  Galileo's views on vertical motion, horizontal motion, and projectile motion
• Aristotelian vs Galilean conceptions

  Comparison and contrast of Aristotle's and Galileo's views on motion
• Galileo Galilei was an Italian physicist who played a major role in the scientific revolution, studied natural forces and conducted theoretical and experimental work on motions of bodies
• Aristotle claimed that heavy and light objects drop in the same way
• Aristotle's two classes of motion

  • Natural motion
  • Violent motion
• Natural motion

  • Smoke rising
• Violent motion

  • Kicked soccer ball
  • Pulled bag
  • Pushed trolley
• According to Aristotle, the sack of rice being pulled by a volunteer experiences a natural motion
• Galileo's view disagrees with Aristotle's theory that objects fall faster in air than water
• Galileo believed that in a vacuum, a cotton ball would fall as fast as a metal ball
• Galileo believed that an object in uniform motion will travel a distance that is proportional to time
• According to Galileo's experiments, motion is uniformly accelerated when speed is proportional to time of travel
• Galileo's concept of a projectile

  A moving object that will continue in motion until acted upon by an external force
• Vertical motion

  Motion that is referred to as natural motion, where the object will move and return to its natural state based on the object's material or composition
• Horizontal motion

  Motion that requires a push or pull to maintain, and stops when the force is removed. This is referred to as violent motion.
• Projectile motion

  Motion that is parallel to the ground until the object falls back to the ground. Aristotle viewed this as a combination of natural and violent motion.
• Aristotle believed that heavy objects fall faster than light ones
• Aristotle's explanation for projectiles continuing to fly after leaving a bow

  The initial motive force transfers to the medium surrounding the object, which then forces the object into a new region and imparts the "power" to act
• In the absence of resistance, objects would fall at the same rate regardless of their weight, according to Galileo
• Galileo found that objects in horizontal motion, if unimpeded, will continue to move without an external force
• Galileo's study of projectile motion

  1. Performed experiments on uniformly accelerated motion using an inclined plane

  2. Quantified the "rate of fall" by measuring distance and time

  3. Deduced that the "rate of fall" is better measured in terms of downward acceleration

  4. Used geometry to describe projectile motion as a combination of constant horizontal motion and accelerated vertical motion

  5. Determined that the path of a projectile is parabolic
• Galileo believed that a projectile is a combination of uniform motion in the horizontal direction and uniformly accelerated motion in the vertical direction
• Galileo's method of studying motion

  1. Measurement of distance and time

  2. Plotting it graphically

  3. Slowing down the "fall" using ramps rather than viscous materials

  4. Measuring motion in two independent directions (horizontal and vertical)

  5. Deducing that the "rate of fall" is better measured in terms of downward acceleration
• Projectile motion

  Combination of uniform motion in the horizontal direction and uniformly accelerated motion in the vertical direction
• Galileo determined that the path of a projectile is parabolic
• Galileo believed that a projectile will continue to move even without an applied force if it is not impeded
• When you shoot a ball in a basketball ring, the ball does not need a force to keep it moving
• Activities to test Aristotle's and Galileo's views

  1. Drop a book and a flat sheet of paper

  2. Drop a book and a sheet of paper crumpled to a ball

  3. Drop a book with a small flat sheet of paper on top of it
• Aristotle's view

  • Heavier objects fall faster than lighter ones
  • Acceleration of a heavy object during free fall is larger than the acceleration of a light object
• Galileo's view

  • Objects of different masses thrown at the same height will reach the ground at the same time in the absence of air resistance
  • Horizontal motion and vertical motion of a projectile are independent of each other
  • All objects regardless of their masses will fall at the same acceleration when dropped at the same height
• Aristotelian conceptions

  • Horizontal motion
  • Vertical motion
  • Projectile motion
• Galilean conceptions

  • Horizontal motion
  • Vertical motion
  • Projectile motion