module 2

• Motion


  A change in position of any mass with respect to time
• Motion occurs all around you. It's easy to recognize but hard to described
• Motion has held the attention of scientists and philosophers since ancient times
• Aristotle's view on vertical motion


  • Heavy objects fall faster than light objects in proportion to their weight
• Galileo's view on vertical motion


  • The motion of a falling body should be nearly dependent of its weight and should have constant acceleration through careful measurements of distances and time requirements
• Physical quantities that describe motion of objects


  • Distance
  • Displacement
  • Speed
  • Velocity
  • Acceleration
  • Free fall
  • Projectile
• Distance


  Length of the part travelled from starting point to final point
• Displacement


  Length of the part travelled from the starting point to final with consideration to the direction
• Speed


  Rate at which distance is covered
• Velocity


  Displacement in a given time interval
• Acceleration


  Measure of how fast the velocity changes with respect to time
• Free fall


  A body in vertical motion where gravity is the only force acting on it
• Projectile


  A body or a particle in two dimensional motion given an initial velocity and it moves along a curved path under the influence of gravity alone
• Aristotle and Galileo were two of the most important historical figures that laid the foundation of motion concepts
• Views on Motion


  • Aristotelian Concept
  • Galilean Concept
• Horizontal motion (Aristotelian)


  Force is required to maintain horizontal motion

  All moving bodies naturally come to rest
• Horizontal motion (Galilean)


  Objects moving in a straight line at a constant speed requires no force to keep them moving

  It will continue in motion due to inertia unless an external force acts on them
• Vertical motion (Aristotelian)


  Freefall is a natural motion occurring due to the tendency of nature to established balance to bring disturbed elements to its natural resting place

  Heavier objects have more earthly elements than lighter ones hence they fall should fall faster. It will take shorter time to reach the ground

  Warmer bodies have an access on fiery elements hence they ascend faster
• Vertical motion (Galilean)


  Objects move downward because gravity disturbs their motion

  The rate of fall or acceleration of an object is independent of their mass

  The motion of falling objects is uniformly accelerated
• Projectile motion (Aristotelian)


  The motion of a projectile is parallel to the ground until it is the object's time to fall back into the ground
• Projectile motion (Galilean)


  A projectile moves two-dimensional in a parabolic path

  The horizontal motion component has zero acceleration (constant speed horizontally) and vertical acceleration is constant
• When air resistance can be neglected, all bodies experience equal acceleration regardless of their size and weight. This constant acceleration g is called the acceleration due to gravity
• Galileo Galilei was regarded as the Father of modern science
• Galileo did many experiments on the concept of Free fall
• Galileo proved that regardless of their masses and air resistance two objects dropped simultaneously will reach the ground at the same time
• Galileo discovered that objects fall with uniform acceleration
• Galileo's Data on a Free Fall Experiment


  • Time (s)
  • Speed (m/s)
  • Acceleration (m/s2)
• The acceleration of the rolling ball increases as the inclined place becomes steeper
• When the inclined plane was positioned vertically, the rolling ball has maximum acceleration
• Uniform or constant acceleration


  Steady, incremental additions of velocity evenly proportionate to time
• Aristotle believed that forces are necessary to keep objects in motion
• Galileo believed that force was not necessary to sustain motion
• Galileo postulated the ball would reach exactly the same height if friction could be eliminated
• A moving object needs no force to keep it moving, when friction is absent
• Before Isaac Newton, Galileo Galilei laid the foundation for the study of force and motion
• Aristotle's concept was that moving objects would stop because the natural state of objects was to be at 'rest'
• Galileo believed that once the ball is in motion, no force is needed to keep it moving except for the force needed to overcome friction
• Newton's First Law of Motion (Law of Inertia) says that the net force on an object is zero, then the object will have zero acceleration implying that the object is either at rest or moving with uniform velocity
• Inertia is the natural inclination of any object to maintain state of rest or to remain in uniform motion in a straight line
• The more mass the object has, the greater is the tendency to resist changes in motion