Chapter 3 Practice Problems, Review, and Assessment
Section 1 Acceleration: Practice Problems
2. Use the v-t graph of the toy train in Figure 9 to answer these questions.
a. When is the train’s speed constant?
b. During which time interval is the train’s acceleration positive?
c. When is the train’s acceleration most negative?
SOLUTION:
a. 5.0 to 15.0 s
b. 0.0 to 5.0 s
c. 15.0 to 20.0 s
ANSWER:
a. 5.0 to 15.0 s
b. 0.0 to 5.0 s
c. 15.0 to 20.0 s
3. Refer to Figure 9 to find the average acceleration of the train during the following time intervals.
a. 0.0 s to 5.0 s
b. 15.0 s to 20.0 s
c. 0.0 s to 40.0 s
SOLUTION:
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ANSWER:
a. 5.0 to 15.0 s
b. 0.0 to 5.0 s
Chapter
3 Practice
c. 15.0
to 20.0 sProblems, Review, and Assessment
3. Refer to Figure 9 to find the average acceleration of the train during the following time intervals.
a. 0.0 s to 5.0 s
b. 15.0 s to 20.0 s
c. 0.0 s to 40.0 s
SOLUTION:
ANSWER:
a.
b.
c.
4. CHALLENGE Plot a v-t graph representing the following motion: An elevator starts at rest from the ground floor
2
of a three-story shopping mall. It accelerates upward for 2.0 s at a rate of 0.5 m/s , continues up at a constant
2
velocity
of-1.0
m/s for
12.0 s, and then slows down with a constant downward acceleration of 0.25 m/s for 4.0 sPage
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it reaches the third floor.
SOLUTION:
ANSWER:
a.
b. 3 Practice Problems, Review, and Assessment
Chapter
c.
4. CHALLENGE Plot a v-t graph representing the following motion: An elevator starts at rest from the ground floor
2
of a three-story shopping mall. It accelerates upward for 2.0 s at a rate of 0.5 m/s , continues up at a constant
2
velocity of 1.0 m/s for 12.0 s, and then slows down with a constant downward acceleration of 0.25 m/s for 4.0 s as
it reaches the third floor.
SOLUTION:
ANSWER:
5. A race car’s forward velocity increases from 4.0 m/s to 36 m/s over a 4.0-s time interval. What is its average
acceleration?
SOLUTION:
ANSWER:
6. The race car in the previous problem slows from 36 m/s to 15 m/s over 3.0 s. What is its average acceleration?
SOLUTION:
ANSWER:
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8. A car is coasting backward downhill at a speed of 3.0 m/s when the driver gets the engine started. After 2.5 s, the
car is moving uphill at 4.5 m/s. If uphill is chosen as the positive direction, what is the car’s average acceleration?
ANSWER:
Chapter
3 Practice Problems, Review, and Assessment
6. The race car in the previous problem slows from 36 m/s to 15 m/s over 3.0 s. What is its average acceleration?
SOLUTION:
ANSWER:
8. A car is coasting backward downhill at a speed of 3.0 m/s when the driver gets the engine started. After 2.5 s, the
car is moving uphill at 4.5 m/s. If uphill is chosen as the positive direction, what is the car’s average acceleration?
SOLUTION:
ANSWER:
Section 1 Acceleration: Review
13. Velocity-Time Graph Sketch a velocity-time graph for a car that goes east at 25 m/s for 100 s, then west at 25 m/s
for another 100 s.
SOLUTION:
ANSWER:
14. Average Velocity and Average Acceleration A canoeist paddles upstream at a velocity of 2.0 m/s for 4.0 s and
then floats downstream at 4.0 m/s for 4.0 s.
a. What is the average velocity of the canoe during the 8.0-s time interval?
b. What is the average acceleration of the canoe during the 8.0-s time interval?
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SOLUTION:
a. Choose a coordinate system with the positive direction upstream.
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Chapter 3 Practice Problems, Review, and Assessment
14. Average Velocity and Average Acceleration A canoeist paddles upstream at a velocity of 2.0 m/s for 4.0 s and
then floats downstream at 4.0 m/s for 4.0 s.
a. What is the average velocity of the canoe during the 8.0-s time interval?
b. What is the average acceleration of the canoe during the 8.0-s time interval?
SOLUTION:
a. Choose a coordinate system with the positive direction upstream.
b.
ANSWER:
a. Choose a coordinate system with the positive direction upstream.
b.
Chapter Assessment
Section 1 Acceleration: Mastering Concepts
54. Give an example of each of the following:
a. an object that is slowing down, but has a positive acceleration
b. an object that is speeding up but has a negative acceleration
c. an object that is moving at a constant speed but has an acceleration
SOLUTION:
a. if forward is the positive direction, a car moving backward at decreasing speed
b. in the same coordinate system, a car moving backward at increasing speed
c. a car that is moving on a circular track at a constant speed
ANSWER:
a. if forward is the positive direction, a car moving backward at decreasing speed
b. inManual
the same
coordinate
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c. a car that is moving on a circular track at a constant speed
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ANSWER:
a. Choose a coordinate system with the positive direction upstream.
Chapter 3 Practice Problems, Review, and Assessment
b.
Chapter Assessment
Section 1 Acceleration: Mastering Concepts
54. Give an example of each of the following:
a. an object that is slowing down, but has a positive acceleration
b. an object that is speeding up but has a negative acceleration
c. an object that is moving at a constant speed but has an acceleration
SOLUTION:
a. if forward is the positive direction, a car moving backward at decreasing speed
b. in the same coordinate system, a car moving backward at increasing speed
c. a car that is moving on a circular track at a constant speed
ANSWER:
a. if forward is the positive direction, a car moving backward at decreasing speed
b. in the same coordinate system, a car moving backward at increasing speed
c. a car that is moving on a circular track at a constant speed
56. If the velocity-time graph of an object moving on a straight path is a line parallel to the horizontal axis, what can you
conclude about the object’s acceleration?
SOLUTION:
When the velocity-time graph is a line parallel to the horizontal axis, the acceleration is zero.
ANSWER:
When the velocity-time graph is a line parallel to the horizontal axis, the acceleration is zero.
Chapter Assessment
Section 1 Acceleration: Mastering Problems
57. Ranking Task Rank the following objects according to the magnitude of the acceleration, from least to greatest.
Specifically indicate any ties. (Level 1)
A. A falling acorn accelerates from 0.50 m/s to 10.3 m/s in 1.0 s.
B. A car accelerates from 20 m/s to rest in 1.0 s.
C. A centipede accelerates from 0.40 cm/s to 2.0 cm/s in 0.50 s.
D. While being hit, a golf ball accelerates from rest to 4.3 m/s in 0.40 s.
E. A jogger accelerates from 2.0 m/s to 1.0 m/s in 8.3 s.
SOLUTION:
From least to greatest magnitude of acceleration: C < E < A < D < B.
A.
B.
C.
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ANSWER:
When the velocity-time graph is a line parallel to the horizontal axis, the acceleration is zero.
Chapter 3 Practice Problems, Review, and Assessment
Chapter Assessment
Section 1 Acceleration: Mastering Problems
57. Ranking Task Rank the following objects according to the magnitude of the acceleration, from least to greatest.
Specifically indicate any ties. (Level 1)
A. A falling acorn accelerates from 0.50 m/s to 10.3 m/s in 1.0 s.
B. A car accelerates from 20 m/s to rest in 1.0 s.
C. A centipede accelerates from 0.40 cm/s to 2.0 cm/s in 0.50 s.
D. While being hit, a golf ball accelerates from rest to 4.3 m/s in 0.40 s.
E. A jogger accelerates from 2.0 m/s to 1.0 m/s in 8.3 s.
SOLUTION:
From least to greatest magnitude of acceleration: C < E < A < D < B.
A.
B.
C.
D.
E.
ANSWER:
From least to greatest magnitude of acceleration: C < E < A < D < B.
59. The graph in Figure 27 describes the motion of an object moving east along a straight path. Find the acceleration of
the object at each of these times: (Level 1)
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a. during the first 5.0 min of travel
b. between 5.0 min and 10.0 min
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ANSWER:
From least to greatest magnitude of acceleration: C < E < A < D < B.
Chapter 3 Practice Problems, Review, and Assessment
59. The graph in Figure 27 describes the motion of an object moving east along a straight path. Find the acceleration of
the object at each of these times: (Level 1)
a. during the first 5.0 min of travel
b. between 5.0 min and 10.0 min
c. between 10.0 min and 15.0 min
d. between 20.0 min and 25.0 min
SOLUTION:
a. Let east be the positive direction.
b.
c.
d.
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ANSWER:
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Chapter 3 Practice Problems, Review, and Assessment
d.
ANSWER:
a. Let east be the positive direction.
= 6.0m/min2 east
b.
c.
d.
= 0.0m/min2
= 2.0m/min2 west
= 4.0m/min2 west
Chapter Assessment
Section 2 Motion with Constant Acceleration: Mastering Problems
68. Refer to Figure 29 to find the magnitude of the displacement during the following time intervals. Round answers to
the nearest meter.
a. t = 5.0 min and t = 10.0 min
b. t = 10.0 min and t = 15.0 min
c. t = 25.0 min and t = 30.0 min
d. t = 0.0 min and t = 25.0 min
SOLUTION:
a.
b. Area (15 m/min)(5 min) = 75 m
c.
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d.
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c.
d.
= 2.0m/min west
= 4.0m/min2 west
Chapter 3 Practice Problems, Review, and Assessment
Chapter Assessment
Section 2 Motion with Constant Acceleration: Mastering Problems
68. Refer to Figure 29 to find the magnitude of the displacement during the following time intervals. Round answers to
the nearest meter.
a. t = 5.0 min and t = 10.0 min
b. t = 10.0 min and t = 15.0 min
c. t = 25.0 min and t = 30.0 min
d. t = 0.0 min and t = 25.0 min
SOLUTION:
a.
b. Area (15 m/min)(5 min) = 75 m
c.
d.
ANSWER:
a. 88 m
b. 75 m
c. 13 m
d. 288 m
Chapter Assessment: Applying Concepts
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78. Explain how you would walk to produce each of the position-time graphs in Figure 30.
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a. 88 m
b. 75 m
c. 13 m
Chapter
3 Practice
Problems, Review, and Assessment
d. 288
m
Chapter Assessment: Applying Concepts
78. Explain how you would walk to produce each of the position-time graphs in Figure 30.
SOLUTION:
(1) Walk in the positive direction at a constant speed. (2) Walk in the positive direction at an increasing
speed for a short time; keep walking at a moderate speed for twice that amount of time; slow down over
a short time and stop; remain stopped; and turn around and repeat the procedure until the original
position is reached.
ANSWER:
(1) Walk in the positive direction at a constant speed. (2) Walk in the positive direction at an increasing
speed for a short time; keep walking at a moderate speed for twice that amount of time; slow down over
a short time and stop; remain stopped; and turn around and repeat the procedure until the original
position is reached.
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