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Physics - College, section 1, Fall 2019
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Serway and Vuille - College Physics 9/e (Homework)

James Finch

Physics - College, section 1, Fall 2019

Instructor: Dr. Friendly

Current Score : 8 / 28

Due : Monday, January 28, 2030 00:00 EST

Last Saved : n/a Saving... ()

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8/28 (28.6%)

Instructions

The WebAssign content for College Physics 9/e by Serway and Vuille includes an extensive bank of more than 5,000 questions including end-of-chapter problems, interactive Active Figure questions, and tutorial problems offering feedback and hints to guide students to content mastery.

What's New in this Edition? Based on their analysis of WebAssign data, the authors identified and enhanced the most frequently assigned problems, ensuring students receive support where they need it most. Denoted in the text by a shaded box around the problem number, each of these problems in Enhanced WebAssign provides students with targeted answer-specific feedback designed to address common misconceptions plus either a Watch It solution video or a Master It interactive tutorial.

Click here for a list of all of the questions coded in WebAssign. This demo assignment allows many submissions and allows you to try another version of the same question for practice wherever the problem has randomized values.

Assignment Submission

For this assignment, you submit answers by question parts. The number of submissions remaining for each question part only changes if you submit or change the answer.

Assignment Scoring

Your last submission is used for your score.

1. –/2 points SerCP9 4.CQ.013. My Notes

Part 1 - Instructor Note

Conceptual Questions At the end of each chapter are approximately a dozen conceptual questions. The Applying Physics examples presented in the text serve as models for students when conceptual questions are assigned and show how the concepts can be applied to understanding the physical world. The conceptual questions provide the student with a means of self-testing the concepts presented in the chapter. Some conceptual questions are appropriate for initiating classroom discussions.
Part 2 - Sample Conceptual Question

In a tug-of-war between two athletes, each pulls on the rope with a force of 260 N. What is the tension in the rope?
N

If the rope doesn't move, what horizontal force does each athlete exert against the ground?
N

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2. 1/1 points | Previous Answers SerCP9 4.MC.010. My Notes

Part 1 - Instructor Note

Multiple-Choice Questions These questions serve several purposes: Some require calculations designed to facilitate students' familiarity with the equations, the variables used, the concepts the variables represent, and the relationships between the concepts. The rest are conceptual and are designed to encourage physical thinking. Finally, many students are required to take multiple-choice tests, so some practice with that form of question is desirable.
Part 2 - Sample Multiple-Choice Question

If an object is in equilibrium, which of the following statements is not true?

The velocity is constant. The speed of the object remains constant. The net force acting on the object is zero. The acceleration of the object is zero. The object must be at rest.

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3. 0/1 points | Previous Answers SerCP9 4.P.010.WI. My Notes

A 4.4-g bullet leaves the muzzle of a rifle with a speed of 334 m/s. What force (assumed constant) is exerted on the bullet while it is traveling down the 0.79-m-long barrel of the rifle?

Your response differs from the correct answer by more than 10%. Double check your calculations. N

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4. –/2 points SerCP9 4.P.030. My Notes

Part 1 - Instructor Note

End of Chapter Questions All questions and problems for this revision were carefully reviewed to improve their variety, interest, and pedagogical value while maintaining their clarity and quality. An extensive set of problems is included at the end of each chapter
Part 2 - Sample End of Chapter Question

A block of mass m = 5.1 kg is pulled up a θ = 21° incline as in the figure with a force of magnitude F = 38 N. (Let the direction of the force be the positive direction.)

(a) Find the acceleration of the block if the incline is frictionless.
m/s²

(b) Find the acceleration of the block if the coefficient of kinetic friction between the block and incline is 0.11.
m/s²

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5. –/4 points SerCP9 4.P.014. My Notes

Part 1 - Instructor Note

Symbolic problems ask students to solve a problem using only symbolic manipulation. The goal is to better train the student to deal with mathematics at a level appropriate to this course. Most students at this level are uncomfortable with symbolic equations, which is unfortunate because symbolic equations are the most efficient vehicle for presenting relationships between physics concepts. Once students understand the physical concepts, their ability to solve problems is greatly enhanced. As soon as the numbers are substituted into an equation, however, all the concepts and their relationships to one another are lost, melded together in the student's calculator. Symbolic problems train the student to postpone substitution of values, facilitating their ability to think conceptually using the equations. An example of a Symbolic problem appears below.
Part 2 - Symbolic Question using PhysPad

An object of mass m is dropped from the roof of a building of height h. While the object is falling, a wind blowing parallel to the face of the building exerts a horizontal constant force F on the object.
(a) How long does it take the object to strike the ground? Express the time t in terms of g and h.
t =

(b) Find an expression in terms of m and F for the acceleration a_x of the object in the horizontal direction (taken as the positive x-direction).
a_x =

(c) How far is the object displaced horizontally before hitting the ground? Answer in terms of m, F, g, and h.
Δx =

(d) Find the magnitude of the object's acceleration while it is falling, using the variables F, m, and g.
a =

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6. –/3 points SerCP9 4.P.029.MI.FB. My Notes

Part 1 - Instructor Note

Enhanced Questions now contain both Enhanced Feedback and Master It! tutorials.

Enhanced Feedback If a student makes one of several common mistakes in the question itself, they will get feedback specific to the mistake they made. If their answer is incorrect but does not meet one of these specific conditions, they will still get generic feedback.

Master It! Tutorials walk students step-by-step through the problem, using different values than have been assigned.

Try some of these values for Part (b) to see what feedback you get!

Incorrect formula

Incorrect answer

44.0

(m₁ + m₂ + m₃)

6.29

Correct formula

Correct answer

F −

m₃F

(m₁ + m₂ + m₃)

18.9

Part 2 - End of Chapter Question with Enhanced Feedback and Master It!

Assume the three blocks (m₁ = 1.0 kg, m₂ = 2.0 kg, and m₃ = 4.0 kg) portrayed in the figure below move on a frictionless surface and a force F = 44 N acts as shown on the 4.0-kg block.

(a) Determine the acceleration given this system.
m/s² (to the right)

(b) Determine the tension in the cord connecting the 4.0-kg and the 1.0-kg blocks.
N

(c) Determine the force exerted by the 1.0-kg block on the 2.0-kg block.
N

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7. –/2 points was SerCP9 4.AF.020. My Notes

Part 1 - Instructor Note

Active Figures build conceptual understanding, allowing students to view animations of figures from the text and visualize phenomena and processes that can't be represented on the printed page. Students can change variables to see the effects, conduct suggested explorations of the principles involved, and receive feedback on related quiz questions.
Part 2 - Sample Active Figure

Active Figure 4.20 The Atwood Machine

Instructions Click 'start' to utilize the following Active Figure.

Display in a New Window Explore
When two objects of unequal masses are suspended on opposite sides of a frictionless pulley with negligible mass, the arrangement is called an Atwood machine. Suppose an Atwood machine has a mass of m₁ = 17.2 kg and another mass of m₂ = 18.6 kg hanging on opposite sides of the pulley. Determine the magnitude of the acceleration of the two objects and the tension in the lightweight cord.

Conceptualize
Imagine the situation pictured in the Active Figure. As one object moves upward, the other object moves downward. Because the objects are connected by an inextensible string, their accelerations must be of equal magnitude.

Categorize
The objects in the Atwood machine are subject to the gravitational force as well as to the forces exerted by the string connected to them. Therefore, we can categorize this problem as one involving two particles under a net force.

Analyze
The free-body diagrams for the two objects are shown in the Active Figure. Two forces act on each object: the upward force exerted by the string and the downward gravitational force. In problems such as this one the pulley is modeled as massless and frictionless, and the tension in the string is the same on both sides of the pulley. If the pulley has mass or is subject to friction, other techniques must be used to take these factors into account.

The signs used in problems such as this require care. When object 1 accelerates upward, object 2 accelerates downward. Therefore, m₁ going up and m₂ going down should be represented equivalently by the same acceleration with the same sign. We can do that by defining our sign convention with up as positive for m₁ and down as positive for m₂.

With this sign convention, the y-component of the net force exerted on object 1 is T − m₁g, and the y-component of the net force exerted on object 2 is m₂g − T.

Applying Newton's second law to m₁ gives the result
(1)
F_y
= T − m₁g = m₁a_y.
Do the same thing for m₂:
(2)
F_y
= m₂g − T = m₂a_y.
The acceleration a_y is the same for both objects. When Equation (1) is added to Equation (2), T cancels and we obtain
(3) −m₁g + m₂g = m₁a_y + m₂a_y.
Solving Equation (3) for a_y and substituting for the given values of m₁ = 17.2 kg and m₂ = 18.6 kg gives
(4)
a_y =
m₂ − m₁
m₁ + m₂
g = m/s².

Substitute Equation (4) into Equation (1) to find T.

T = m₁(g + a_y) =
2m₁m₂
m₁ + m₂
g = N.

Finalize
The acceleration given by Equation (4) can be interpreted as the ratio of the magnitude of the unbalanced force (m₂ − m₁)g to the total mass (m₁ + m₂) of the system, as expected from Newton's second law. Notice that the sign of the acceleration depends on the relative masses of the two objects.

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8. –/6 points SerCP9 4.AE.007. My Notes

Part 1 - Instructor Note

Active Examples, based on the worked examples in the text, guide students through the process needed to master a concept. A related question at the end of these examples provides a twist on the text problem to test students' understanding. These questions include hints and feedback to help students solve the problem.

Try It! The "Exercise" portion of the Active Examples help overcome common misconceptions. If a student enters an answer based on a common mistake, students will receive feedback specific to that mistake. If their answer is incorrect but does not meet one of these specific conditions, they will still get generic numerical feedback as to how far off they are.

Try some of these values for the first answer box in the "Exercise" section to see what feedback you get! (Let T be the tension force and w_s be the weight of the sled.)

Incorrect formula

Incorrect answer

61.5

sin(30°)

123

cos(30°)

− w_s

0.0141

Correct formula

Correct answer

sin(30°)

− w_s

Part 2 - Sample Active Example

EXAMPLE 4.7 Sled on a Frictionless Hill

(a) A sled tied to a tree on a friction less hill. (b) A diagram of forces acting on the sled.

Goal Use the second law and the normal force in an equilibrium problem.

Problem A sled is tied to a tree on a frictionless, snow-covered hill, as shown in figure (a). If the sled weighs 77.0 N, find the magnitude of the tension force T with arrow

exerted by the rope on the sled and that of the normal force n with arrow

exerted by the hill on the sled.

Strategy When an object is on a slope, it's convenient to use tilted coordinates, as in figure (b), so that the normal force n with arrow

is in the y-direction and the tension force T with arrow

is in the x-direction. In the absence of friction, the hill exerts no force on the sled in the x-direction. Because the sled is at rest, the conditions for equilibrium, ΣF_x = 0 and ΣF_y = 0 apply, giving two equations for the two unknowns—the tension and the normal force.

SOLUTION

Apply Newton's second law to the sled, with a with arrow

= 0.

_g = 0

Extract the x-component from this equation to find T. The x-component of the normal force is zero, and the sled's weight is given by mg = 77.0 N.

F_x

T + 0 − mg sin θ = T − (77.0 N)(sin 30.0°) = 0

38.5 N

Write the y-component of Newton's second law. The y-component of the tension is zero, so this equation will give the normal force.

F_y

0 + n − mg cos θ = n − (77.0 N)(cos 30.0°) = 0

66.7 N

LEARN MORE

Remarks Unlike its value on a horizontal surface, n is less than the weight of the sled when the sled is on the slope. This is because only part of the force of gravity (the x-component) is acting to pull the sled down the slope. The y-component of the force of gravity balances the normal force.

Question Consider the same scenario on a hill with a steeper slope.

Would the magnitude of the tension in the rope get larger, smaller, or remain the same as before?

The magnitude of the tension force would be greater. The magnitude of the tension force would be smaller. The magnitude of the tension force would remain the same.

How would the normal force be affected?

The magnitude of the normal force would be greater. The magnitude of the normal force would be smaller. The magnitude of the normal force would remain the same.

PRACTICE IT

Use the worked example above to help you solve this problem. A sled is tied to a tree on a frictionless, snow-covered hill, as shown in Figure (a). If the sled weighs 71.0 N, find the magnitude of the tension force T with arrow

exerted by the rope on the sled and that of the normal force n with arrow

exerted by the hill on the sled.

T	=	N
n	=	N

EXERCISE HINTS: GETTING STARTED | I'M STUCK!

Use the values from PRACTICE IT to help you work this exercise. Suppose a child of weight w climbs onto the sled. If the tension force is measured to be 61.5 N, find the weight of the child and the magnitude of the normal force acting on the sled.

w	=	N
n	=	N

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9. 4/4 points | Previous Answers SerCP9 Q1.1.002. My Notes

How many significant figures are there in each of the following?

(a) 9.26 ± 0.01

(b) 3.553 ± 0.004

(d) 0.0225

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10. 3/3 points | Previous Answers SerCP9 Q1.1.001.Tutorial. My Notes

1.1: SIGNIFICANT FIGURES

Part 1 - Multiplication and Division

Dividing 2.54 by 1.3, a calculator produces 1.9538462. However, it would be very imprecise to report 1.9538462 as the answer because it would be leading others astray since this many significant figures in the result implies that the data used is accurate to at least that same number of significant figures. The least accurate number, 1.3, is known to two significant figures; therefore, the answer should be rounded to two significant figures, 2.0, where 1.95 is rounded up to 2.0.

A general rule is that your answer from the product or division of two numbers should never have more significant figures than the number possessing the least number of significant figures.

VIDEO EXAMPLE 1: EXAMPLE 1-1

Note that 0.0000356 has only three significant figures. The four zeroes between the decimal point and the 3 show only the position of the decimal point and are not considered significant.
Part 2 - Addition and Subtraction

Addition and subtraction demand care when involving decimals because both are sensitive to the placement of the decimal point.

VIDEO EXAMPLE 2: EXAMPLE 1-2

In the following example, we find the sum of two numbers with different significant figures.

VIDEO EXAMPLE 3: EXAMPLE 1-3

Usually, the formulas you will need to evaluate will not be as simple as the preceding examples, and they will contain many numbers, with few, if any, having the same number of significant figures. You could round off at each step, which would involve quite a bit more time, or you could wait until the end of the calculation and then round off the answer to the required significant figures. However, to avoid introducing a compounding round-off error into your calculations, you should wait until the end of your calculation to round the result to the correct number of significant figures. In other words, leave all your calculations in the calculator until the final result is displayed and then round that result.

Carry out the following arithmetic operations. (Enter your answers to the correct number of significant figures.)

(a) the sum of the measured values 521, 39.8, 0.70, and 5.5

WebAssign will check your answer for the correct number of significant figures.

(b) the product 1.2 × 2.247

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Welcome, demo@demo

Serway and Vuille - College Physics 9/e (Homework)

Current Score : 8 / 28

Due : Monday, January 28, 2030 00:00 EST

Last Saved : n/a Saving... ()

Instructions

Assignment Submission

Assignment Scoring

Part 1 - Instructor Note

Part 2 - Sample Conceptual Question

Part 1 - Instructor Note

Part 2 - Sample Multiple-Choice Question

Part 1 - Instructor Note

Part 2 - Sample End of Chapter Question

Part 1 - Instructor Note

Part 2 - Symbolic Question using PhysPad

Part 1 - Instructor Note

Part 2 - End of Chapter Question with Enhanced Feedback and Master It!

Part 1 - Instructor Note

Part 2 - Sample Active Figure

Part 1 - Instructor Note

Part 2 - Sample Active Example

Part 1 - Multiplication and Division

Part 2 - Addition and Subtraction