Aristotle, Galileo and Motion

• Aristotle's writings greatly influenced Galileo, who studied Aristotle's theory of motion at the University of Pisa.
• Galileo later developed his own thought experiment about motion.
• Motion is defined as a change in position of any mass with respect to time.
• The lesson will compare Aristotelian and Galilean views on vertical, horizontal, and projectile motion.

Key Concepts of Motion

• Distance is the length of the path traveled from the starting point to the final point and is measured in meters (m).
• Displacement is the length of the path traveled with consideration of direction, also measured in meters (m).
• Speed is the rate at which distance is covered, measured in meters per second (m/s).
• Velocity is displacement over a time interval, quantified in meters per second (m/s).
• Acceleration measures how velocity changes over time, quantified in meters per second squared (m/s²).
• Free fall is vertical motion where gravity is the only acting force, and can involve upward, downward, or zero initial velocity.
• A projectile is a body in two-dimensional motion with an initial velocity, moving along a curved path under gravity.
• Aristotle and Galileo's views on motion, though different, both contributed to the progress of science.

Contrasting Views on Motion

• Horizontal Motion

  • Aristotle: Requires force to maintain and bodies naturally come to rest.
  • Galileo: Objects in motion stay in motion without force, due to inertia unless acted upon by an external force.

• Vertical Motion

  • Aristotle: Freefall is natural as nature restores balance, heavier objects fall faster, and warmer objects ascend faster.
  • Galileo: Objects move downward due to gravity, the rate of fall is independent of mass, and the motion of falling objects is uniformly accelerated.

• Projectile Motion

  • Aristotle: Projectile motion is parallel to the ground until the object falls.
  • Galileo: Projectiles move two-dimensionally in a parabolic path, with constant horizontal speed and constant vertical acceleration.

• In modern times, it's understood that when air resistance is negligible, all bodies have equal acceleration due to gravity.

Uniform Acceleration

• Galileo is considered the Father of Modern Science for linking theory with experiment, especially concerning free fall.
• Galileo used inclined planes to study falling objects and reduce acceleration to something easily measurable.

Galileo's Findings on Free Fall

• Objects in a vacuum fall with uniform acceleration.
• Galileo proved that objects dropped simultaneously (neglecting air resistance) reach the ground at the same time and fall with uniform acceleration.
• A ball rolling down an inclined plane increases its speed by the same value every second.
• The acceleration increases as the inclined plane becomes steeper, reaching maximum acceleration when vertical.
• Galileo concluded that falling objects have uniform acceleration, regardless of mass when there's no air resistance.
• Constant acceleration for Galileo meant steady, incremental additions of velocity, evenly proportionate to time.

Constant Velocity vs Constant Acceleration

• Constant velocity involves constant speed in a constant direction.
• Constant acceleration involves a uniform change in velocity over time along a straight line.
• Positive velocity indicates movement in the positive direction.
• Negative velocity indicates movement in the negative direction.
• Positive acceleration indicates the object is speeding up.
• Negative acceleration indicates the object is slowing down.

Force and Horizontal Motion

• Aristotle thought forces were needed to keep objects in motion.
• Galileo demonstrated that force isn't needed to sustain motion.
• Galileo observed that a ball rolling on downward-sloping places gains speed, and loses speed on upward-sloping places.
• With smoother planes, the ball rolled closer to the initial height illustrating the effects of friction, and he postulated that without friction, the ball would reach the same height.
• A moving object needs no force to keep moving when friction is absent, due to inertia.

Free Fall Experiment

• Designed to explain uniform acceleration.
• Materials needed: bond paper, notebook, coin and a drawing of the setup.
• Crumple one piece of paper and drop it alongside a flat sheet, and alongside a notepad.
• Pair it with a coin and perform a similar test.
• Consider the factors affecting the fall of objects based on observations.