Serway et al - Physics, Asia-Pacific Edition (Homework)

James Finch

Physics - College, section 1, Fall 2019

Instructor: Dr. Friendly

Current Score : 14 / 21

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

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14/21 (66.7%)

Instructions

Create your course assignments by selecting questions from our bank of end-of-section exercises, as well as enhanced interactive examples with videos.

Students can view and hear additional instruction through the 2-5 minute Watch It links. Students will also find helpful links to online excerpts from their textbook, tutorials, and videos.

Every problem includes a link to the appropriate section of a complete interactive eBook, (also available through a dynamic table of contents from the student's WebAssign homepage), allowing students to highlight and take notes as they read.

- relevant textbook pages

- videos of worked examples

- tutorials

Many problems include detailed stepped-out solutions, available to students at each instructor's discretion.

In this assignment we present several textbook question types found in Physics, Asia-Pacific Edition 1/e by R. Serway, J. Jewett, K. Wilson, A. Wilson published by Brooks/Cole.

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.

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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.

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1. –/3 points was SerPhysAUS1 5.AF.013. My Notes

Active Figure - Terminal Speed

Instructions: Utilize the following active figure depicting a sphere encountering a resistive force proportional to its speed to complete the following sections.

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A small sphere of mass 110 g is released from rest in a large vessel filled with oil where it experiences a resistive force proportional to its speed. The sphere approaches a terminal speed of 4.9 cm/s.

(a) Determine the time constant τ.
(b) Determine the time interval required for the sphere to reach 36% of its terminal speed.

Conceptualize
With the help of the Active Figure, imagine dropping the sphere into the oil and watching it sink to the bottom of the vessel.

Categorize
We model the sphere as a particle under a net force, with one of the forces being a resistive force that is proportional to the speed of the sphere.

(A) Determine the time constant τ. Analyze From v_t = mg/b, evaluate the coefficient b:

b =

v_t

110 g (980 cm/s²)

4.9 cm/s

= 22000.00 g/s

Therefore, the time constant τ is given below

τ =

= s

(B) The time required for the sphere to reach 36% of its terminal speed. Analyze The speed of the sphere as a function of time is given by

v(t) = v_T(1 - e^-t/τ)

To find the time t at which the sphere is traveling at a speed of v = 0.36 v_T, we set v to that value and solve for t:

0.36 v_t = v_t (1 - e^-t/τ)

(1 - e^{- t/τ}) = 36/100

e^-t/τ = 0.64

- t

= ln(0.64) = - 0.45

t = 0.45 τ = s

t = ms

Finalize The sphere reaches 36% of its terminal speed in a very short time interval. You can also see this behavior, for example, by watching a marble sink in a bottle of clear shampoo.

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2. –/3 points SerPhysAUS1 5.CQ.006. My Notes

Consider a small raindrop and a large raindrop falling through the atmosphere.

(a) Compare their terminal speeds.

The larger drop has higher terminal speed. The larger drop has lower terminal speed. Both raindrops have the same terminal speed.

(b) What are their accelerations when they reach terminal speed?

a_{larger drop}	=	m/s²
a_{smaller drop}	=	m/s²

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3. –/1 points SerPhysAUS1 5.P.010. My Notes

One side of the roof of a building slopes up at 30.5°. A roofer kicks a round, flat rock that has been thrown onto the roof by a neighborhood child. The rock slides straight up the incline with an initial speed of 15.0 m/s. The coefficient of kinetic friction between the rock and the roof is 0.350. The rock slides 10.0 m up the roof to its peak. It crosses the ridge and goes into free fall, following a parabolic trajectory above the far side of the roof, with negligible air resistance. Determine the maximum height the rock reaches above the point where it was kicked.
m

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4. –/6 points SerPhysAUS1 5.P.012. My Notes

A skydiver of mass 80.5 kg jumps from a slow-moving aircraft and reaches a terminal speed of 45.0 m/s.

(a) What is her acceleration when her speed is 30.0 m/s?

magnitude	m/s²
direction

(b) What is the drag force on the skydiver when her speed is 45.0 m/s?

magnitude	N
direction

magnitude	N
direction

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5. –/3 points SerPhysAUS1 5.P.018.soln. My Notes

A motorboat cuts its engine when its speed is 7.9 m/s and coasts to rest. The equation describing the motion of the motorboat during this period is v = v_ie^-ct, where v is the speed at time t, v_i is the initial speed at t = 0, and c is a constant. At t = 19.2 s, the speed is 5.00 m/s.

(a) Find the constant c.
s^-1

(b) What is the speed at t = 40.0 s?
m/s
(c) Differentiate the expression for v(t) and thus show that the acceleration of the boat is proportional to the speed at any time.

a = -ce^-ct a = cv a = cv_ie^-ct a = ce^-ct a = cv_i a = -cv

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6. –/1 points SerPhysAUS1 5.P.042. My Notes

A truck is moving with constant acceleration a up a hill that makes an angle ϕ with the horizontal as in the figure below. A small sphere of mass m is suspended from the ceiling of the truck by a light cord. If the pendulum makes a constant angle θ with the perpendicular to the ceiling, what is a? (Use any variable or symbol stated above along with the following as necessary: g.)
a =

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7. –/3 points SerPhysAUS1 5.P.043.MI. My Notes

Because the Earth rotates about its axis, a point on the equator experiences a centripetal acceleration of 0.033 7 m/s², whereas a point at the poles experiences no centripetal acceleration. Assume the Earth is a uniform sphere and take g = 9.800 m/s².

(a) If a person at the equator has a mass of 72.6 kg, calculate the gravitational force (true weight) on the person. (Give your answer to four significant figures.)

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

N

(b) Calculate the normal force (apparent weight) on the person. (Give your answer to four significant figures.)

N

(c) Which force is greater?

the gravitational force the normal force

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8. –/1 points SerPhysAUS1 5.QQ.001. My Notes

You press your physics textbook flat against a vertical wall with your hand. What is the direction of the friction force exerted by the wall on the book?

upwards downwards out from the wall into the wall there is no frictional force

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Serway et al - Physics, Asia-Pacific Edition (Homework)

Current Score : 14 / 21

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

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

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