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Average Velocity and Average Speed
1 Represent and reason
car stops for a red light. The light turns green and the car moves forward for 3 seconds at a steadily increasing
speed. During this time, it travels 20 meters. The car then travels at a constant speed for another 3 seconds for a
distance of 30 meters. Finally, when approaching another red light, the car steadily slows to a stop during the next
3 s in 15 meters.
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a) Draw a dot diagram that describes this process.
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c) What is the total path length that the car traveled?
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d) What is the average speed of the car? (To find the average speed. you need to divide the total path length
traveled by the total time of travel.)
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e) How does the total average speed for the entire 9 seconds compare to the average speed for each of the 3second intervals? Why are the average speeds different? Explain.
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Copyright 2008. Rutgers. The State University of New Jersey.
42
Therkorn Unit 1: Kinematics
What is the average velocity? (To find the average velocity, you need to divide the displacement traveled by
total time of travel.)
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g) A car traveled for 15 s at 10 rn/s and another 15 s at 20 rn/s. What is the average speed?
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h) The same car traveled 200 m at 10 rn/s and another 200 m at 20 rn/s
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Homework
epresent and reason
A and B.
,isider the two position-Versus-time graphs below for objects
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B
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Time
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Time (s)
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that of A in graph 2?
a) How does the motion of the object A in graph 1 compare to
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motion of object B in graph 2?
b) How does the motion of object B in graph 1 compare to the
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c) Which object has the smaller magnitude in velocity in graph 2?
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d) Describe what is happening at the point where the function of object
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age of Mathematics while doing Physics Adapted from A. Van Heuvelen
PUM Kinematics Lesson 8: Reading and Writing in the Langu
Jersey.
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PUM I Kinematics Lesson 8: Reading and Writing in the Language of Mathematics while doing Physics Adapted from A. Van Heuvelen and E. Etkina. Active
Learning Guide. Addison Wesley. San Francisco, 2006 © Copyright 2008, Rutgers, The State University of New Jersey.
59
Rei,resent and reason
Position vs Time
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40
20
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10
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30
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time (mm)
The position of an object is represented in the graph above.
a) Describe the motion in words and sketch a dot diagram.
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b) What is the average speed of the object for the different time intervals: 0-10 mm, 10-20 mm, and 20-30 mm?
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PUM I Kinematics Lesson 5: Average Velocity and Average Speed Adapted from A. Van Heuvelen and E.
44
Etkina, Active Learning Guide, Addison Wesley, San Francisco, 2006 © Copyright 2008, Rutgers, The State University of New Jersey.
Therkrn Unit 1: Kinematics
c What is the average sDeed of the object during the entire 30 mm?
d) What is the average velocity for the entire 30 mm?
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PUM Kinematics Lesson 5: Average Velocity and Average Speed Adapted from A. Van Heuvelen and E.
Etkina, Active Learning Guide, Addison Wesley, San Francisco, 2006 © Copyright 2008, Rutgers, The State University of New Jersey.
45
Homework
Represent and reason
Position vs. Time
40
35
30
25
20
15
10
5
5
10
20
15
25
30
35
time (mm)
The position of an object is represented in the graph above.
a) Describe the motion in words and
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b) What is the average speed of the object for the different time intervals: 0-10 mm, 10-20 mm, 20-30 mm, and
i 0-40 mm.
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PUM Kinematics I Lesson 5: Average Velocity and Average Speed
I
Mapted froi’n A. Van Heuvelen and E.
Etkina, Active Learning Guide, Addison Wesley, San Francisco, 2006 © Copyright 2008, Rutgers, The State University of New Jersey.
46
Th rkorn Unit 1: Kinematics
c) What is the average speed for the object during the entire 40 mm? What is the average velocity during that
same interval? Howta the object move so that the answers to these two questions are different from each
other?
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d) During which time interval was the average speed the largest?
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PUM Kinematic Lesson 5: Average Velocity and Average Speed Adapted from A. Van Heuvelen and E.
Etkina, Active Learning Guide, Addison Wesley, San Francisco, 2006 © Copyright 2008, Rutgers, The State University of New Jersey.
47