One-Dimensional Kinematics
Position, Distance, Displacement
Average Speed/Velocity
Acceleration
Online Tools/Announcements
• http:/aw-bc.com/walker/
• Online homework coming soon
• QUIZ over Chapter 2 one week from Thursday (
9/6 )
• “Chapter Summary” may be useful for each
chapter
2-1 Position, Distance, and Displacement
Before describing motion, you must set up a coordinate
system – define an origin and a positive direction.
2-1 Position, Distance, and Displacement
The distance is the total length of travel ( m ); if you
drive from your house to the grocery store and back, you
have covered a distance of 8.6 mi.
2-1 Position, Distance, and Displacement
Displacement is the change in position. If you drive from
your house to the grocery store and then to your friend’s
house, your displacement is 2.1 mi and the distance you
have traveled is 10.7 mi.
2-2 Average Speed and Velocity
The average speed is defined as the distance traveled divided by the
time the trip took: Average speed = distance / elapsed time
2-2 Average Speed and Velocity
Average velocity = displacement / elapsed time
If you return to your starting point, your average velocity is zero.
Conceptual Checkpoint 2-1
Conceptual Checkpoint 2-1
2-2 Average Speed and Velocity
Graphical Interpretation of Average Velocity
The same motion, plotted one-dimensionally and as an x-t
graph:
2-4 Acceleration
Average acceleration:
(2-5)
2-4 Acceleration
Graphical Interpretation of Average and Instantaneous
Acceleration:
2-4 Acceleration
Acceleration (increasing speed) and deceleration (decreasing
speed) should not be confused with the directions of velocity
and acceleration:
THURSDAY!!
• Go to lab stations as soon as you get to class
HOMEWORK ( show work )!!
• EVERYONE:
• Pg 48 ( #s 4,10 ) Pg 49 ( # 14 )
• AP:
• Pg 48 ( # 6 ) Pg 49 ( # 23 )
Pg 50 ( # 32 )
2-5 Motion with Constant Acceleration
If the acceleration is constant, the velocity changes linearly:
(2-7)
Average velocity:
2-5 Motion with Constant Acceleration
Average velocity:
(2-9)
Position as a function of time:
(2-10)
(2-11)
Velocity as a function of position:
(2-12)
2-5 Motion with Constant Acceleration
The relationship between position and time follows a
characteristic curve.
2-6 Applications of the Equations of Motion
Hit the Brakes!
2-7 Freely Falling Objects
Free fall is the motion of an object subject only to the
influence of gravity. The acceleration due to gravity is
a constant, g.
2-7 Freely Falling Objects
An object falling in air is subject to air resistance (and
therefore is not freely falling).
HOMEWORK!!
• Pg. 50 ( #44 )
• Pg. 51 ( # 49 )