1. Free Fall

2. Free fall The motion of an object falling freely under the influence of gravity  “Free” means free from any effects other than GRAVITY  “Fall” means any motion under the influence of gravity alone (whether the object is dropped from rest, thrown upward, or thrown downward)

3.  Acceleration ! Each second a freely falling object falls about 10 m/s faster than it did before.  Galileo figured out that if air is neglected, ALL objects (regardless of size, mass, shape, etc.) accelerate at an exact rate of 9.8 m/s/s (called “ g ”).  The direction of acceleration is always DOWN (towards the Earth)

4.  Value of “g” varies depending on one’s location and altitude  North Pole, 90°N latitude, g = 9.832 m/s 2  Hong Kong, 30°N latitude, g = 9.793 m/s 2  Quito, Ecuador, 0° latitude, g = 9.780 m/s 2  For this class, g = - 9.8 m/s 2 (on earth!)  All a’s in kinematic equations replaced with g’s

5.  Paper and the Book  Feather and Brick on the Moon Feather and Brick on the Moon  Galileo off the side of the Leaning Tower Galileo off the side of the Leaning Tower Do heavier objects really fall faster than lighter objects?

7. For now, consider only the up and down motion!

8. zero reference point on the way up: slowing down v is positive a is negative at the top: stopped v is zero a is negative on the way down: speeding up v is negative a is negative