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Physics - College, section 1, Fall 2019
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Serway & Jewett - Physics for S&E Tech Update 9/e (Homework)

James Finch

Physics - College, section 1, Fall 2019

Instructor: Dr. Friendly

Current Score : 19 / 78

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

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

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Question

Points

1	2	3	4	5	6	7	8	9	10	11	12
9/20	0/15	–/1	4/8	1/15	–/2	1/1	–/2	–/1	1/6	1/5	2/2

Total

19/78 (24.4%)

Instructions

Create your course assignments by selecting questions from our bank of end-of-section exercises, enhanced interactive examples and tutorials.

While doing their homework, students can link to the relevant interactive examples from the book and work through them again and again for additional practice before answering the question.

Read It

- Every problem includes a link to the appropriate section of a complete interactive eBook.

- Select problems feature a detailed Master It tutorial, guiding students through prompted steps to solve the specific problem.

Students can view 2--5-minute narrated Watch It videos, recorded by Physics instructors to help students solve select problems.

In this assignment we present several textbook question types found in Chapter 5 on The Laws of Motion in Physics for Scientists and Engineers Technology Update 9/e by Raymond A. Serway and John W. Jewett, Jr., published by Cengage Learning.

Enhanced for This Technology Update
Question 1 is an Integrated Tutorial question. It strengthens students' skills by guiding them through the problem-solving steps identified in their textbook. Tutorials take students through the process, asking questions they will learn to ask themselves when faced with new problems.

Enhanced for This Technology Update
Question 2 is a PreLecture Exploration. Using HTML5 interactive simulations, students can make predictions, change parameters, and observe results. Each PreLecture Exploration presents an engaging simulation based on a relevant scenario and then asks conceptual and analytic questions, guiding students to a deeper understanding and helping promote a robust physical intuition. This is the perfect resource for a flipped classroom or for professors looking for new ways to increase student engagement and interest in the material prior to lecture.

Enhanced for This Technology Update
Question 3 is a problem with a complete solution. Hundreds of end-of-chapter problems include fully worked out solutions to help students better understand problem-solving strategies as applied to specific problems.

Question 4 is an Active Example which guides students through the process needed to master a concept. A "Master It" question at the end provides a twist on the in-text Example to test student understanding.

Question 5 is an Analysis Model Tutorial problem, which guides students through every step of the problem-solving process, driving them to see the important link between the situation in the problem and the mathematical representation of the situation.

Question 6 is a Conceptual Question, designed to help students test their understanding of physical concepts as they work through each chapter.

Question 7 is an Objective Question.

Question 8 is a Master It problem with a complete tutorial.

Questions 9, 10, and 11 are traditional end-of-chapter problems with symbolic answer entry.

Question 12 is a problem with a Watch It video.

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.

The answer key and solutions will display after the first submission for demonstration purposes. Instructors can configure these to display after the due date or after a specified number of submissions.

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. 9/20 points | Previous Answers SerPSET9 5.IT.002. My Notes

2. 0/15 points | Previous Answers SerPSET9 5.PLE.002. My Notes

This question has several parts that must be completed sequentially. If you skip a part of the question, you will not receive any points for the skipped part, and you will not be able to come back to the skipped part.

When two massive objects are suspended on opposite sides of a pulley, the arrangement is called an Atwood machine. Two friends, Makena and Dani, are studying physics together, and they decide to delve further into understanding this arrangement.

In this simulation, the cord that connects the two masses is ideal; that is, it is inextensible (does not stretch) and its mass is negligible. Also, the pulley is frictionless with negligible mass, and any air resistance can be neglected. The forces and accelerations of the two masses are shown, along with the tension in the cord.

The sign convention for motion is defined as shown by the arrows. Makena and Dani can change the mass of m₁ and m₂ by using the sliders. They then can click "start" to set the system in motion.

Click here to open the simulation in a new window.

Part 1 of 13 - Accelerations in an Atwood Machine

Dani and Makena examine the figure shown.

Which of Dani's statements is correct, given what she knows about this system?

"Mass m₁ will accelerate downward, whereas mass m₂ will remain stationary." "Mass m₂ will accelerate downward, whereas mass m₁ will remain stationary." "Both masses m₁ and m₂ will accelerate downward." correct

"It is possible that masses m₁ and m₂ will accelerate, and if they do, the accelerations of both will be equal in magnitude, but we can't know for sure unless we have more information."

Dani is incorrect. She does not realize that the rope connects the masses, so if one accelerates, both will accelerate.

Now the friends consider the situation for which the mass m₁ is initially moving downward. Makena and Dani discuss the acceleration in this case. Which of Makena's statements could be correct?

"Mass m₁ will accelerate downward, whereas mass m₂ will remain stationary." "Mass m₂ will accelerate downward, whereas mass m₁ will remain stationary." "Both mass m₁ and m₂ will accelerate downward." correct

"It is possible that masses m₁ and m₂ will accelerate, and if they do, the accelerations of both will be equal in magnitude, but we cannot know for sure unless we have more information."

Makena is incorrect. She has not realized that the rope connects the masses, so if one accelerates, both will accelerate.

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3. –/1 points SerPSET9 5.P.007. My Notes

The distinction between mass and weight was discovered after Jean Richer transported pendulum clocks from Paris, France, to Cayenne, French Guiana in 1671. He found that they quite systematically ran slower in Cayenne that in Paris. The effect was reversed when the clocks returned to Paris. How much weight would a 77.0 kg person lose in traveling from Paris, where g = 9.8095 m/s², to Cayenne, where g = 9.7808 m/s²?
N

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4. 4/8 points | Previous Answers SerPSET9 5.AE.007. My Notes

Example 5.7 One Block Pushes Another

(a) A force is applied to a block of mass m₁, which pushes on the second block of mass m₂. (b) The forces acting on m₁. (c) The forces acting on m₂.

Two blocks of masses m₁ and m₂, with m₁ > m₂, are placed in contact with each other on a frictionless, horizontal surface as in figure (a). A constant horizontal force vector F

is applied to m₁ as shown.

(A) Find the magnitude of the acceleration of the system.

(B) Determine the magnitude of the contact force between the two blocks.

SOLVE IT

(A) Find the magnitude of the acceleration of the system.

Conceptualize Conceptualize the situation by using figure (a) and realize that both blocks must experience the same acceleration because they are in contact with each other and remain in contact throughout the motion.

Categorize We categorize this problem as one involving a particle under a net force because a force is applied to a system of blocks and we are looking for the acceleration of the system.

Analyze First model the combination of two blocks as a single particle under a net force. Apply Newton's second law to the combination in the x direction to find the acceleration (Use the following as necessary: F, m₁, and m₂):

F_x = F = (m₁ + m₂)a_x

(1) a_x =

Finalize The acceleration given by Equation (1) is the same as that of a single object of mass m₁ + m₂ and subject to the same force.

(B) Determine the magnitude of the contact force between the two blocks.

Conceptualize The contact force is internal to the system of two blocks. Therefore, we cannot find this force by modeling the whole system (the two blocks) as a single particle.

Categorize Now consider each of the two blocks individually by categorizing each as a particle under a net force.

Analyze We construct a diagram of forces acting on the object for each block as shown in figures (b) and (c), where the contact force is denoted by

From figure (c), we see that the only horizontal force acting on m₂ is the contact force

₁₂

(the force exerted by m₁ on m₂), which is directed to the right.

Apply Newton's second law to m₂:

(2)

F_x = P₁₂ = m₂a_x

Substitute the value of the acceleration a_x given by Equation (1) into Equation (2) (Use the following as necessary: F, m₁, and m₂):

(3) P₁₂ = m₂a_x =

Finalize This result shows that the contact force P₁₂ is less than the applied force F. The force required to accelerate block 2 alone must be less than the force required to produce the same acceleration for the two-block system.

To finalize further, let us check this expression for P₁₂ by considering the forces acting on m₁, shown in figure (b). The horizontal forces acting on m₁ are the applied force vector F

to the right and the contact force

₂₁

to the left (the force exerted by m₂ on m₁). From Newton's third law,

₂₁

is the reaction force to

₁₂,

so P₂₁ = P₁₂.

Apply Newton's second law to m₁:

(4)

F_x = F − P₂₁ = F − P₁₂ = m₁a_x

Solve for P₁₂ and substitute the value of a_x from Equation (1):

P₁₂ = F − m₁a_x = F − m₁

m₁ + m₂

m₂

m₁ + m₂

This result agrees with Equation (3), as it must.

MASTER IT HINTS: GETTING STARTED | I'M STUCK!

Three blocks are in contact with one another on a frictionless, horizontal surface as in the figure below. A horizontal force vector F

is applied to m₁, where m₁ = 1.52 kg, m₂ = 3.73 kg, m₃ = 4.92 kg, and F = 18.5 N. (Take the +x direction to be to the right.)

(a) Find the acceleration of the blocks.

1.82

m/s²

(b) Find the net force on each block.

F_{1, net}	=	2.76 N
F_{2, net}	=	6.79 N
F_{3, net}	=	8.95 N

P₁₂	=	15.7 What force must m1 exert directly on m₂ to accelerate the rest of the blocks as calculated in part (a)? N
P₂₃	=	8.95 What force must m₂ exert directly on m₃ to accelerate it as calculated in part (a)? N

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5. 1/15 points | Previous Answers SerPSET9 5.AMT.033. My Notes

A bag of cement weighing 361 N hangs in equilibrium from three wires as suggested in the figure. Two of the wires make angles

θ₁ = 65.0°

and

θ₂ = 44.0°

with the horizontal. Assuming the system is in equilibrium, find the tensions T₁, T₂, and T₃ in the wires.

Part 1 of 8 - Conceptualize:

Look carefully at the figure. Which force do you expect to be larger,

T₁ or T₂?

Should we expect that

T₁ and T₂

will each be larger than the weight of the bag because only a component of their magnitude is in the vertical direction? Or should they each be smaller because they work together to hold up the bag? Or could one force be larger than the weight and one smaller? We'll choose a standard coordinate system with x horizontal and y vertical.

Part 2 of 8 - Categorize:

(1) What analysis model correctly describes the knot, that is, the point at which all three forces meet, and is most useful for solving this problem?

particle under constant velocity particle under a net force correct

particle in equilibrium particle under constant acceleration none of the above

Correct. The knot is subject to forces but is not moving.

(2) The ring at the top of the strap, where the rope carrying force

T₃

is attached, is also a particle in equilibrium. Therefore, the tension

T₃ = N.

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6. –/2 points SerPSET9 5.CQ.007. My Notes

A person holds a ball in her hand.

(a) Identify all the external forces acting on the ball and the Newton's third-law reaction force to each one. (Select all that apply.)

The force due to gravity of the earth pulling down on the ball; the reaction force is the force due to gravity of the ball pulling up on the earth. The force of the hand pushing up on the ball; the reaction force is ball pushing down on the hand. The force due to gravity of the earth pulling down on the hand; the reaction force is the force due to gravity of the hand pulling up on the earth. No forces act on the ball.

(b) If the ball is dropped, what force is exerted on it while it is falling? Identify the reaction force in this case. (Ignore air resistance.)

No forces act on the ball while it is in free fall. The force of the hand pushing up on the ball; the reaction force is ball pushing down on the hand. The gravity due to the earth; the reaction force is the gravity due to the ball pulling on the earth. The force due to gravity of the earth pulling down on the hand; the reaction force is the force due to gravity of the hand pulling up on the earth.

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7. 1/1 points | Previous Answers SerPSET9 5.OQ.002. My Notes

In the figure below, a locomotive has broken through the wall of a train station. During the collision, what can be said about the force exerted by the locomotive on the wall?

The force exerted by the locomotive on the wall was larger than the force the wall could exert on the locomotive. The force exerted by the locomotive on the wall was less than the force exerted by the wall on the locomotive. The wall cannot be said to "exert" a force; after all, it broke. correct

The force exerted by the locomotive on the wall was the same in magnitude as the force exerted by the wall on the locomotive.

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8. –/2 points SerPSET9 5.P.011.MI. My Notes

An electron of mass 9.11

10^-31 kg has an initial speed of 2.20

10⁵ m/s. It travels in a straight line, and its speed increases to 7.20

10⁵ m/s in a distance of 4.80 cm. Assume its acceleration is constant.

(a) Determine the magnitude of the force exerted on the electron.
N

(b) Compare this force (F) with the weight of the electron (F_g), which we ignored.

F_g

Need Help?

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9. –/1 points SerPSET9 5.P.012. My Notes

Besides the gravitational force, a 3.75-kg object is subjected to one other constant force. The object starts from rest and in 1.20 s experiences a displacement of (4.55î − 3.30ĵ) m, where the direction of ĵ is the upward vertical direction. Determine the other force.
vector F

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10. 1/6 points | Previous Answers SerPSET9 5.P.013. My Notes

11. 1/5 points | Previous Answers SerPSET9 5.P.015. My Notes

Two forces,

₁ = (2.10î − 5.30ĵ) N

and

₂ = (4.05î − 5.65ĵ) N,

act on a particle of mass 1.80 kg that is initially at rest at coordinates

(+2.35 m, +4.05 m).

(a) What are the components of the particle's velocity at t = 10.8 s?
vector v

75.35

$webMathematica generated answer key$ m/s

(b) In what direction is the particle moving at t = 10.8 s?

-60.7

° counterclockwise from the +x-axis

(c) What displacement does the particle undergo during the first 10.8 s?
Δ vector r

406.98

$webMathematica generated answer key$ m

(d) What are the coordinates of the particle at t = 10.8 s?

x	=	202 Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. m
y	=	-351 Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. m

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12. 2/2 points | Previous Answers SerPSET9 5.P.018. My Notes

A force

applied to an object of mass m₁ produces an acceleration of 3.30 m/s². The same force applied to a second object of mass m₂ produces an acceleration of 2.00 m/s².

(a) What is the value of the ratio m₁/m₂?

0.606

(b) If m₁ and m₂ are combined into one object, find its acceleration under the action of the force F with arrow

1.25

m/s²

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Case 1:	if particle B was at rest before the collision, and
Case 2:	if particle B was moving toward particle A with a speed equal to that of particle A.

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