1. Acceleration Due to Gravity
Free fall - falling under influence of gravity w/o ______ ____________
Distance proportional to time squared
Speed changes linearly with time
The ____________________________ is the same for all objects and is often represented by the letter ____
g = 9.8 m/s2 toward the Earth.
air
resistance
acceleration due to gravity g

2. Falling objects zero 9.8 m/s2 symmetry
The velocity at the top of the path is _______
The acceleration of the object throughout the motion is always ____________
Trajectories show up and down ____________
zero
9.8 m/s2
symmetry

3. Falling objects
For a falling body, a = g = 9.8 m/s2 down

4. Falling objects
Notice that the distance the object falls during each second is larger than the distance that it fell in the previous second… WHY?

5. Acceleration Due to Gravity
d = ½ at2
vf = vi + at
a = g = 9.8 m/s2 down or -9.8 m/s2
Remember that if up is labeled as the ________________, down must be labeled as the ________________
The velocity at the top of an object’s path is _____ when it is in __________.
positive direction
negative direction
zero
freefall

6. An object is dropped from the top of the Willis Tower, which is 443 meters tall. How long will it take the object to reach the ground?
How fast is the object travelling when it lands on the ground?
d = ½ a t2
d = m
a = m/s2
- 443 m = ½ (-9.8 m/s2) t2
t = ?
- 443 m = (-4.9 m/s2) t2
t = 9.51 s
vf = vi + a t
d = m
vf = 0 m/s + (-9.8 m/s2)(9.51 s)
a = m/s2
vf = m/s
t = 9.51 s
Why is the answer negative?
vf = ?
Because the object is moving down!
vi = 0 m/s