1. Free Fall
DEMO: Crumbled Paper & Tennis Ball
Tower of PISA

2. Elephant & Feather Experiment
Imagine that you release an
elephant and a feather from the
Tower of Pisa. Assuming that
the air resistance is negligible, which object hits the ground first?
Video: Do cats always fall on their feet? Discuss.

3. Acceleration Due to Gravity
Every object on the earth experiences a common force: the force due to gravity.
This force is always directed toward the center of the earth (downward).
The acceleration due to gravity is relatively constant near the Earth’s surface.
Earth Fg g

4. Acceleration Due to Gravity
In a vacuum, all objects fall with same acceleration.
Equations for constant acceleration apply as usual.
Near the Earth’s surface:
a = g = 9.81 m/s2 or 32 ft/s2
Directed downward (usually negative).

5. Accepted Value g=9.81 m/s2
The value of weight Fg=mg changes with latitude because Earth is not a perfect sphere

6. Gravity on the Other Planets