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Chabay and Sherwood - Matter and Interactions 4/e (Homework)

James Finch

Physics - College, section 1, Fall 2019

Instructor: Dr. Friendly

Current Score : 8 / 22

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
1/1 1/1 –/6 2/2 3/3 –/3 –/2 1/3 –/1
Total
8/22 (36.4%)

  • Instructions

    In this assignment we present questions from chapter 2 of Matter and Interactions 4th edition, by Ruth Chabay and Bruce Sherwood, published by John Wiley & Sons, representing various question types found in the book.

    Every problem includes a link to the appropriate section of a complete eBook (also available through a dynamic table of contents from the student's WebAssign homepage).

    Many problems include solutions, available to students at each instructor's discretion.

    View the complete list of WebAssign questions available for this textbook. 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.

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1. 1/1 points  |  Previous Answers MI4 2.Q.003. My Notes
Question Part
Points
Submissions Used
1
1/1
11/50
Total
1/1
 
You observe three carts moving to the left. Cart A moves to the left at nearly constant speed. Cart B moves to the left, gradually speeding up. Cart C moves to the left, gradually slowing down. Which cart or carts, if any, experience a net force to the left? (Select all that apply.)
Correct: Your answer is correct.



Solution or Explanation
If the speed is constant, the net force must be zero. If the speed is decreasing, the net force must be opposite to the motion. Only if the net force is in the same direction as the motion will the speed increase.

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2. 1/1 points  |  Previous Answers MI4 2.Q.007. My Notes
Question Part
Points
Submissions Used
1
1/1
1/50
Total
1/1
 
A ball moves in the direction of the arrow labeled a in the figure. The ball is struck by a stick that briefly exerts a force on the ball in the direction of the arrow labeled c in the figure. Which arrow best describes the direction of
Δp,
 the change in the ball's momentum?
Correct: Your answer is correct. seenKey

c
A direction rosette shows a upward, b upper right at 45 degrees, c rightward, d lower right at 45 degrees, e downward, f lower left at 45 degrees, g leftward, and h upper left at 45 degrees.


Solution or Explanation
Start from the Momentum Principle,
Δp = FnetΔt.
 Since Δt is a scalar, the direction of the change in momentum
Δp
 is the same as the direction of the net force
Fnet.

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3. –/6 points MI4 2.4.021. My Notes
Question Part
Points
Submissions Used
1 2 3 4 5 6
–/1 –/1 –/1 –/1 –/1 –/1
0/50 0/50 0/50 0/50 0/50 0/50
Total
–/6
 
Use the approximation that
v ≈ pf/m
 for each time step.

You throw a metal block of mass 0.20 kg into the air, and it leaves your hand at time
t = 0
 at location
0, 2, 0
 m
 with velocity
2.5, 4.5, 0
 m/s.
 At this low velocity air resistance is negligible. Using the iterative method shown in Section 2.4 with a time step of 0.05 s, calculate step by step the position and velocity of the block at
t = 0.05 s,
t = 0.10 s,
 and
t = 0.15 s.
 (Express your answers in vector form.)
x(t = 0.05 s) = 
m
v(t = 0.05 s) = 
m/s
x(t = 0.10 s) = 
m
v(t = 0.10 s) = 
m/s
x(t = 0.15 s) = 
m
v(t = 0.15 s) = 
m/s

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4. 2/2 points  |  Previous Answers MI4 2.5.026. My Notes
Question Part
Points
Submissions Used
1 2
1/1 1/1
2/50 1/50
Total
2/2
 
The driver of a car traveling at a speed of 15.5 m/s slams on the brakes and comes to a stop in 3.3 s. If we assume that the car's speed changed at a constant rate (constant net force), find the following.
(a) What was the car's average speed during this 3.3 s interval?
Correct: Your answer is correct. seenKey

7.75

 m/s

(b) How far did the car go in this 3.3 s interval?
Correct: Your answer is correct. seenKey

25.6

 m

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5. 3/3 points  |  Previous Answers MI4 2.5.030. My Notes
Question Part
Points
Submissions Used
1 2 3
1/1 1/1 1/1
2/50 2/50 2/50
Total
3/3
 
A cart rolls with low friction on a track. A fan is mounted on the cart, and when the fan is turned on, there is a constant force acting on the cart. Three different experiments are performed:
(a) Fan off: The cart is originally at rest. You give it a brief push, and it coasts a long distance along the track in the +x direction, slowly coming to a stop.
(b) Fan forward: The fan is turned on, and you hold the cart stationary. You then take your hand away, and the cart moves forward, in the +x direction. After traveling a long distance along the track, you quickly stop and hold the cart.
(c) Fan backward: The fan is turned on facing the "wrong" way, and you hold the cart stationary. You give it a brief push, and the cart moves forward, in the +x direction, slowing down and then turning around, returning to the starting position, where you quickly stop and hold the cart.
The figure displays four graphs of px (numbered 1–4), the x component of momentum, vs. time. The graphs start when the cart is at rest, and end when the cart is again at rest. Match the experiment with the correct graph.
fan off     Correct: Your answer is correct. seenKey

2
fan forward     Correct: Your answer is correct. seenKey

4
fan backward     Correct: Your answer is correct. seenKey

1

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6. –/3 points MI4 2.5.034. My Notes
Question Part
Points
Submissions Used
1 2 3
–/1 –/1 –/1
0/50 0/50 0/50
Total
–/3
 
A soccer ball is kicked at an angle of 64° to the horizontal with an initial speed of 15 m/s. Assume for the moment that we can neglect air resistance.
(a) For how much time is the ball in the air?
s

(b) How far does it go (horizontal distance along the field)?
m

(c) How high does it go?
m

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7. –/2 points MI4 2.6.042. My Notes
Question Part
Points
Submissions Used
1 2
–/1 –/1
0/50 0/50
Total
–/2
 
Use the approximation that
vavg = pf/m
 for each time step.

A spring with a relaxed length of 25 cm and a stiffness of 12 N/m stands vertically on a table. A block of mass 78 g is attached to the top of the spring. You pull the block upward, stretching the spring until its length is now 28.7 cm, hold the block at rest for a moment, and then release it. Using a time step of 0.1 s, predict the position and momentum of the block at a time 0.2 s after you release the block. (Assume the +y direction is upward. Express your answers in vector form.)
r
 		=
m
p
 		=
kg · m/s

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8. 1/3 points  |  Previous Answers MI4 2.6.044. My Notes
Question Part
Points
Submissions Used
1 2 3
–/1 –/1 1/1
0/50 0/50 1/50
Total
1/3
 
Use the approximation that
vavg = pf/m
 for each time step.

A paddle ball toy consists of a flat wooden paddle and a small rubber ball that are attached to each other by an elastic band (figure). You have a paddle ball toy for which the mass of the ball is 0.013 kg, the stiffness of the elastic band is 0.865 N/m, and the relaxed length of the elastic band is 0.295 m. You are holding the paddle so the ball hangs suspended under it, when your cat comes along and bats the ball around, setting it in motion. At a particular instant the momentum of the ball is
−0.02, −0.01, −0.02
 kg · m/s,
 and the moving ball is at location
−0.2, −0.61, 0
 m
 relative to an origin located at the point where the elastic band is attached to the paddle.
(a) Determine the position of the ball 0.1 s later, using a Δt of 0.1 s. (Express your answer in vector form.)
r
 =
m

(b) Starting with the same initial position
−0.2, −0.61, 0
 m
 and momentum
−0.02, −0.01, −0.02
 kg · m/s
,
 determine the position of the ball 0.1 s later, using a Δt of 0.05 s. (Express your answer in vector form.)
r
 =
m

(c) If your answers are different, explain why.
     Correct: Your answer is correct.

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9. –/1 points MI4 2.9.046. My Notes
Question Part
Points
Submissions Used
1
–/1
0/50
Total
–/1
 
A proton has mass
1.7 ✕ 10−27 kg.
 What is the magnitude of the impulse required to increase its speed from
0.994c
 to
0.997c?

N · s

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