Kinematics – The study of motion
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Kinematics – The study of motion
DEVIL PHYSICSTHE BADDEST CLASS ON
CAMPUS
PRE-DP PHYSICS
LSN 2-7: FALLING OBJECTS
Questions From Reading Activity?
Objectives
Understand that, within certain limits, the acceleration due to gravity on the surface of the Earth is constant and acts toward the Earth’s center.
Know that the value of the acceleration due to gravity on the surface of the Earth is 9.81 m/s2
Objectives Understand how
Equations 2-10a to 2-10c can be modified for motion due to gravity as follows: These equations
assume that the acceleration due to gravity is constant and air resistance is negligible.
2
)(2
21
0
020
2
200
0
vvv
yygvv
gttvyy
gtvv
Objectives
Understand the importance of consistency in choosing a frame of reference and choosing which directions are positive and negative during problem solving.
Solve problems involving free-falling objects.
Video: Force of Gravity
Let’s Experiment
Let’s Experiment
What did we learn? Things fall at the same rate =
gravitational acceleration is constant The acceleration is approximately equal
to 9.81 m/s2
Galileo
At a given location on the Earth and in the absence of air resistance, all objects fall with the same constant acceleration.
This is the acceleration due to gravity, g.
g ≈ 9.80 m/s2 or 32 ft/s2 The acceleration due to gravity is
always toward the center of the earth.
Gravity Varies
Location Elevation g
New York 0 9.803
San Francisco 100 9.800
Denver 1650 9.796
Pike’s Peak 4300 9.789
Equator 0 9.780
North Pole 0 9.832
Gravity Varies
Why does gravity vary?
Gravity Varies
Why does gravity vary?
221
r
mMGF
So What Does This All Mean?
So What Does This All Mean? All of the equations we developed for
horizontal motion can be used for vertical motion Substitute g = 9.80 m/s2 for a Change x to y to represent vertical
displacement You now have to decide which direction
is positive (up or down) and which is negative
Make sure that your value for g (positive or negative) matches the direction
So What Does This All Mean?Horizontal Equations
Vertical Equations
2
)(2
21
0
020
2
200
0
vvv
yygvv
gttvyy
gtvv
2
)(2
21
0
020
2
200
0
vvv
xxavv
attvxx
atvv
Let’s Try Some Problems
Summary Review
Do you understand that, within certain limits, the acceleration due to gravity on the surface of the Earth is constant and acts toward the Earth’s center?
Do you know that the value of the acceleration due to gravity on the surface of the Earth is 9.81 m/s2?
Summary Review Do you understand
how Equations 2-10a to 2-10c can be modified for motion due to gravity as follows: These equations
assume that the acceleration due to gravity is constant and air resistance is negligible.
2
)(2
21
0
020
2
200
0
vvv
yygvv
gttvyy
gtvv
Summary Review
Do you understand the importance of consistency in choosing a frame of reference and choosing which directions are positive and negative during problem solving?
Can you solve problems involving free-falling objects?
QUESTIONS?
#32-45
Homework
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