The document discusses free fall, which is when the only force acting on an object is gravity. It explains that in free fall, all objects accelerate at 9.81 m/s^2 toward the center of the Earth. Various examples are provided of objects in free fall, including apples falling from trees and balls being thrown upwards or dropped. Kinematic equations are also presented for calculating velocity, acceleration, distance, and time in free fall situations.

1. An object that the
only force acting on
it is gravity
Mr. P

2. Gravity accelerates all objects down regardless if they are going
up, going down, stopped, or going sideways. An object that the
only force acting on it is gravity is in
Free Fall.

3. An object is in free fall if the only force acting on it is gravity,
doesn’t happen though, near surface of earth there is air resistance!

4. An airplane can simulate free fall
by flying in a parabolic path

5. All freely falling objects
accelerate at 9.81 m/s2 near the
surface of the earth
All are pulled down at the same
rate regardless of their mass and
direction of motion.
( Ignoring air resistance )
2
9.81 /
a m s
 
a g
 

6. Without air resistance With air resistance
Which falls faster without
air resistance?

7. http://faculty.rmwc.edu/tmichalik/movies/tree.mpeg
Galileo dropped a
cannonball and a musket ball
simultaneously from a tower, and
observed that they both hit the
ground at the same time. This
contradicted Aristotle's long-
accepted idea that heavier
objects fell faster.

8. f i
2 2
f i
2
1
i 2
1
f i
2
1. v = v + at
2. v = v + 2ad
3. d = v t + at
4. d = (v + v ) t
To solve free fall
problems use the
kinematic equations and:
1. a = -9.8 m/s2
2. Dropped let vi =0
3. At top let vf =0

10. All of the following are in free fall, on the way
down, up, or sideways

11. Note the lengths of the velocity and acceleration vectors at different
times. (The upward and downward paths of the ball are horizontally
Displaced for illustration purposes.)

12. Velocity vs. Time
For an object thrown straight up at 20 m/s
Acceleration vs. Time
-9.81 m/s2
20 m/s
-20 m/s
-30 m/s
link

14. The slope of a velocity vs time
graph for an object in free fall
near the surface of the earth
will always be -9.81 m/s2.

16. EXAMPLE:
An apple falls from rest from a tree and
takes 1.5 seconds to reach the floor:
a) How high up did it fall from?
b) What is its velocity just before it hits the ground?
a = - 9.81 m/s2

17. A flea can jump to a vertical height of 4cm, find:
a. The initial velocity the pest leaves the ground
b. The time the flea takes to reach its maximum height
2 2
2 2
2
0 2( 9.8 / )(.04 )
.88 /
f i
i
i
v v ad
v m s m
v m s
 
  
 
2
0 .88 / ( 9.8 / )
.09sec
f i
v v at
m s m s t
t
 
  


18. "A ball is thrown straight upward from the top of a cliff with an
initial velocity of 15 m/sec. Assuming the ball just misses the edge
of the cliff on its way down, how fast is it going just before it hits the
ground which is 35 m below the ball's starting point?"
35 m

20. A construction worker
accidentally drops a brick
from a high scaffold.
a. What is the velocity of the
brick after 4.0 s?
b. How far does the brick fall
during this time?