AP Physics - Vertical Kinematics

History - Vertical Motion

Aristotle’s Theory of motion (4th Century B.C.)

  • Matter made up of 5 elements

    • Light

    • Fire

    • Air

    • Water

    • Earth

  • Natural Motion

    • Each element had a natural state and would seek that state if possible

      • Natural state of motion is at rest

    • Doesn’t move based on forces

  • Violent Motion

    • Force was present

  • Idea that heavier objects fall faster came from this idea

  • Limitations to Theory

    • Any object after release would quickly reach some final speed for the remainder of fall

      • Reasoned that heavier objects fall faster

Galileo’s Theory of Motion

  • Questioned early Greek observations

  • Studied freely falling objects

    • He felt this was the key to understanding all observable motion in nature

    • Formed hypothesis that all objects fall at the same constant rate

      • proved mathematically

      • proved indirectly with inclined plane

Acceleration Due to Gravity

  • Gravity’s Acceleration (Not gravity itself)

    • -9.80 m/s²

    • -980 cm/s²

    • -32 ft/s²

  • All objects fall at the same rate in a vacuum

    • No air resistance

    • Apparent difference in fall is due to air resistance

  • Terminal velocity is a constant speed achieved when the weight of a falling object is equal to the force of air resistance

    • weight = air resistance

  • Freely Falling Body = zero air resistance