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Falling Objects
Falling Objects
What Factors Affect the Rate at Which An Object Falls?
Mass
Surface Area
Anything in my Box
Folded Folders
Period 3 - Select Your Factor!
2 Mass
3 Surface Area
4 Mass
5 Surface Area
6 Mass
Period 1 - Select Your Factor!
1 Mass
2 Surface Area
3 Surface Area
4 Surface Area
5 Mass
6 Mass
7 Mass
8 Surface Area
Design and conduct an experiment to see how your factor affects the acceleration of a falling object!
What Did We Learn About Falling Objects?
On your white board, identify three key ideas that you figured out from
our activities!
What Did We Learn About Falling Objects?
Key Ideas about Falling Objects
They experience a constant acceleration!
The force of gravity causes this acceleration
When the only force acting on an object is gravity, we say that the object is in free fall.
How Do We Know It’s Constant Acceleration?
Which graph best represents the displacement of a ball tossed up into the air?
Disp
lace
men
t (m
)
Time (s)
Disp
lace
men
t (m
)
Time (s)
+
-
Disp
lace
men
t (m
)
Time (s)
+
-
1 2 3
If the displacement looks like this…
Disp
lace
men
t (m
)Time (s)
What does the velocity graph look like?
Velo
city
(m/s)
Time (s)
+
-
If the velocity graph looks like this…
What does the acceleration graph look like?
Velo
city
(m/s)
Time (s)
+
-A
ccel
erat
ion
(m/s2 )
Time (s)
+
-
What is the acceleration due to gravity?Group Acceleration of Dropped Ball Acceleration of Tossed Ball
1 -8.8108 m/s^2 -8.7372 m/s^2
2 -5.4276 m/s^2 -7.249 m/s^2
3 - 3.9174 m/s^2 -0.2311 m/s^2
4 -9.92 m/s^2 -8.26 m/s^2
5 -11.68 m/s^2 -10 m/s^2
6 -9.7134 m/s^2 -10.588 m/s^2
7 -8.9514 m/s^2 -8.9274 m/s^2
8 -8.88 m/s^2 -9.315 m/s^2
Average = -9.05 m/s2 Average = -9.01 m/s2
What is the acceleration due to gravity?
At What Rate Do Objects Fall?
When an object is in free fall, it accelerates at a constant rate of 9.8 m/s2.
What about the Mass of the Object?
Mass has no influence on the rate at which
an object falls!
All object’s in free fall fall at a rate of 9.8 m/s2!
Are You Sure??
If a feather and an elephant were dropped from the top of a building at the same time, would they reach the ground
at the same time?
The elephant and feather are not in free fall!
They experience air resistance!
Air ResistanceHow does surface area affect the rate of falling?
The greater the surface area, the greater the air resistance!
Mathematical Models of Free Fall
Because objects in free fall are falling at a constant acceleration, the kinematic
equations still apply!
Let’s Try One For Practice!Let’s say a cannonball with a mass of 5.4 kg is released from rest at the top of the Tower of Pisa, which is 56 meters tall.
How far has the ball fallen in 2 seconds?
vo = 0 m/s
ag = -9.8 m/s
Info: vo = 0 m/s ag = -9.8 m/s t = 2 seconds yo = 0 m y = ?
Let’s Try One For Practice!
y = 1/2(9.8 m/s2)(2 s)2
Info: vo = 0 m/s ag = -9.8 m/s t = 2 seconds yo = 0 m y = ?
vo = 0 m/s
ag = -9.8 m/s
y = 19.6 m Would this be different for a falling bus?
How About Another One?Let’s say an object is tossed upward with a velocity of 5.0 m/s. What is the maximum height it will reach
before turning back around?
Info: vo = 5 m/s ag = -9.8 m/s vf = 0 m/s yo = 0 m y = ?
vo = 5 m/s
ag = -9.8 m/s
How Did You Do?vo = 5 m/s
ag = -9.8 m/s
Info: vo = 5 m/s ag = -9.8 m/s vf = 0 m/s yo = 0 m y = ?
y = 1.28 m
How Long Would It Take to Get Here?
How Did You Do?
vo = 5 m/s
ag = -9.8 m/s
Info: vo = 5 m/s ag = -9.8 m/s vf = 0 m/s t = ?
t = 0.51 s
Don’t Forget!Topic Sections Questions
Displacement & Velocity 2.1 & 2.2 1, 2, 5, 6, 9, 10
Acceleration 2.3 14, 19, 23
Graphical Analysis 2.7 68, 69, 70
Kinematic Equations 2.4 & 2.5 24, 27, 33, 38
Free Fall 2.6 47, 50 51 62
