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Unformatted text preview: ﬁ AP Physics 1 20 5 m l m Ch7HW15 ‘ Itemi Romurces v Item 1 While working on her bike, Amanita turns it upside
down and gives the front wheel a counterclockwise
spin. lt spins at approximately constant speed for a
few seconds. During this portion of the motion, she
records the x and y positions and velocities, as well as
the angular position and angular velocity, for the point Figure 1 Y (”’2 < Item 2 A merry—go—round is rotating at constant angular speed.
Two children are riding the merrygoround: Ana is riding
at point A and Bobby is riding at point B. (Figure 1) Figure‘l v of1 ( ‘ > Part A Which of the graphs corresponds to x position versus time? Graph F Hints MyAnswers Give Up Review Part B Correct Part B Which of the graphs corresponds to angular position versus time? Graph A DI Hints mAnswers Give Up Review Part Part A Which child moves with greater magnitude of linear velocity? \ J Ana has the greater magnitude of linear velocity.
as Bobby has the greater magnitude of linear velocity.
._ ,1 Both Ana and Bobby have the same magnitude of linear velocity. U Hints mAnswers Give Up Review Part Correct The linear velocity is oﬁen just referred to as the velocity. The tangential velocity and radial velocity are
components of the linear velocity. In this scenario, since the merrygo—round has a constant angular
velocity, the radial velocity is zero, therefore the tangential velocity is equal to the linear velocity. Part B Who moves with greater magnitude of angular velocity? = u Ana has the greater magnitude of angular velocity.
L Bobby has the greater magnitude of angular velocity. \0: Both Ana and Bobby have the same magnitude of angular velocity. [:] Hints MyAnswers Give Up ReviewFart (— Item 2
Who moves with greater magnitude of tangential acceleration? A merry—go—round is rotating at constant angular speed.
Two children are riding the merrygoround: Ana is riding U Ana has the greater magnitude of tangential acceleration.
at point A and Bobby is riding at point B. Figure 1) 0 Bobby has the greater magnitude of tangential acceleration. (0) Both Ana and Bobby have the same magnitude of tangential acceleration. :1 Hints MyAnswers Give Up ReviewFart —an < r , I
Correct
Both Ana and Bobby are maintaining a constant speed, so they both have a tangential acceleration ofzero
(thus they are equal)!
Part D Who has the greater magnitude of centripetal acceleration? 0 Ana has the greater magnitude of centripetal acceleration. it) Bobby has the greater magnitude of centripetal acceleration. U Both Ana and Bobby have the same magnitude of centripetal acceleration. . Hints mAnswers Give Up Review Part ,_ Who moves with greater magnitude of angular acceleration? 0 Ana has the greater magnitude of angular acceleration.
0 Bobby has the greater magnitude of angular acceleration.
{'3 Both Ana and Bobby have the same magnitude of angular acceleration. :] Hints MyAnswers Give Up ReviewParl Correct Both Ana and Bobby are maintaining a constant angular velocity so they both have an angular
acceleration of zero (thus they are equal)! Provide Feedback QMasteri’rigPhyés: Ch 7 HW15  Guogle Chrome_ 3 physics.com/myct/itemView?assig nmentProbIemID=60383 555&offset=next AP Physics 1 2015 Ch 7 HW15 Item 3 — u—m ism Help l Close Remurces v (t prevtous l 3 of 15 I next » Item 3 Figure 1) The ﬁgure shows angular position versus time
graphs for six different objects. Figure1 7 of1 < ‘ > Part A Rank these graphs on the basis of the angular velocity of each object. Rank positive angular velocities as larger than negative angular velocities. Rank from largest to smallest. To rank items as equivalent, overlap them. JIIIIU largest I I smallest
sMasteri’rigPhyas: Ch 7 HW15 7 Guogle Chrome_ ﬁ physics.com/myct/itemView?assig nmentProblemID=60383 555&of‘fset=next AP Physics 1 20 5 Ch 7 HW15 . Item 3 _ —u gm Help l Close Resources v «prevtous l 30f15 I next» Item 3 Figure 1) The ﬁgure shows angular position versus time
graphs for six different objects. Part B Rank these graphs on the basis of the angular acceleration of the object. Rank positive angular accelerations as larger than negative angular accelerations. Rank from largest to smallest. To rank items as equivalent, overlap them. Figure1 7 of1 < l > JIIJJU largest I I smallest QMamzﬁsphtéscwMSGueleCImms — I— m 4' w a physics.com/myct/itemView?assig nmentProbIemID=60383 S76&offset=next AP Physics 1 2015 m l Close
on 7 HW15 Item 4
(t prevtous l 4 of 15 I next »
Item 4
Part A As you ﬁnish “stafﬁng to your favorite compact disc If the CD rotates clockwise at 500 rpm (revolutions per minute) while the last song is playing, and then spins down to (CD), the CD in the player slows down to a stop. zero angular speed in 2.60 s with constant angular acceleration, what is as. the magnitude of the angular acceleration Assume that the CD spins down with a constant of the CD, as it spins to a step? angular acceleratton. Express your answer in radians per second squared. a= 20.1 rad/s2 Hints MyAnswers Give Up ReviewPart U Correct Part B How many revolutions does the CD make as it spins to a stop? Express your answer using three signiﬁcant ﬁgures. :J Hints MyAnswers Give Up ReviewPart 10.3 revolutions sMasteri’rigPhyas: Ch 7 HW15 * Guogle Chrome_
ﬁ physics.com/myct/itemView?assig nmentProblemID=60383 550&of‘fset=next AP Physics 1 20 5 we l Close
—Ch7HW15 . Item5 «prevtous l 5of15 I next» P rtA ‘
tem5 a Rank these forces (A through F) on the basis of the magnitude of the torque they apply to the wrench,
measured about an axis centered on the bolt. The wrench in the ﬁgure has six forces of equal magnitude acting on it. (Figure 1) Rank from largest to smallest. To rank items as equivalent, overlap them.
r
Figure 1 v of 1 < ‘ > I I." largest I I smallest game...” A —— d! ._ m a
AP Physics 1 20
on 7 HW15 Item 6 « preVious l 6 of 15 I next » Help l c Item 6
Part A
(J_Fi UTE 1) The ﬁgure shows a simple model Of a What is the moment of inertia I of this assembly about the axis through which it is pivoted? seesaw. These consist of a planklrod of mass mI and
length 23: allowed to pivot freely about its center (or Express the moment of inertia in terms of mI , m1, m2. and 2:. Keep in mind that the length oi the rod central axis), as shown in the diagram. A small sphere i5 2% "0t ﬁt
of mass m1 is attached to the leﬂ end of the rod, and
a small sphere of mass m2 is attached to the right v Figure 1 v of 1 < , Hints MyAnswers Give Up ReviewFart 9—0 Part B M ’"r I "'2 Suppose that the rod is held at rest horizontally and then released. (Throughout the remainder of this problem,
your answer may include the symbol I, the moment of inertia of the assembly, whether or not you have
answered the ﬁrst part correctly.) pivot
What is the angular acceleration a of the rod immediately after it is released? Take the counterclockwise direction to be positive. Express (1 in terms of some or all of the variables
mr,m1,m2,x,1,andg. SMamriﬁsPhﬁxcwmmwsmiledmm. CA — ,_ m a physics.com/myct/itemView?assig nmentProbIemID=60383 566&of‘fset=next AP Physics 1 2
W Item6 «preVious l 6of15 I next» Help l Close Item 6 Part B . . Suppose that the rod is held at rest horizontally and then released. (Throughout the remainder of this problem,
W) The ﬁgureshows a Simple model Of a your answer may include the symbOI I , the moment of inertia of the assembly, whether or not you have
seesaw. These con5ist of a plank/rod of mass mI and answered the ﬁrst a n correctl ) length 2m allowed to pivot freely about its center (or p y. central axis), as shown in the diagram. A small sphere . . . . . . 7
of mass 7111 is attached to the Ieﬂ end of the rod, and What is the angular acceleration a of the rod Immediately after it is released.
a small sphere of mass m2 is attached to the right v Take the counterclockwise direction to be positive. Express (1 in terms of some or all of the variables mr,m1.m2,z,I,andg. Figure 1 v of 1 ( , ‘ Hints mAnswers GiveUp ReviewFart Correct
0 Substituting for I , the value obtained in Part A yields a : (ml’m2)9 % +1111 +1112): '
A large angular acceleration is often desirable. This can be accomplished by making the connecting rod
light and short (since both mr and :1: appear in the denominator of the expression for a). For a seesaw, on the other hand, mI and a: are usually chosen to be as large as possible, while making sure that the
"rod" does not get too heavy and unwieldy. This ensures that the angular acceleration is quite low. pivot Provide Feedback swam“; A —— d! ,_ m a
AP Physics 1 20
on 7 HW15 Item 8 « prevtous I 8 of 15 I next » Help I c Item 8
Part A TWP identical uniform 50“ spheres are attached by a Rank the moments of inertia of this object about the axes indicated.
solid uniform thin rod, as shown in Figure 1) . The rod
lies on a line connecting the centers of mass of the
two spheres. The axes A, B, C, and D are in the plane
of the page (which also contains the centers of mass of the spheres and the rod), while axes E and F v Rank from largest to smallest. To rank items as equivalent, overlap them. largest I I smallest Figure 1 v of 1 < , I: The correct ranking cannot be determined. Hints MyAnswers Give Up ReviewFart — QMamriﬁgPhﬁxChvmseeuoélecmome. A I— d‘ i m a
AP Physics 1 2
W Item 10 «previous I 10 of15 I next» Help I Close Item 10 Part A
If there is no slipping, a frictional force must exist between the wheels and the ground. In what direction does
Figure 1) The car shown in the ﬁgure has mass m the frictional force from the ground on the wheels act? Take the positive x direction to be to the right. (this includes the mass of the wheels). The wheels
have radius r, mass mw, and moment of inertia I : kmwr2 . Assume that the axles apply the same
torque ‘r to all four wheels. For simplicity, also assume 91 positive x direction
that the weight is distributed uniformly so that all the V ‘ ‘ negative xdirection :1 Hints mAnswers Give Up ReviewFart Figure 1 v of 1 ( , Correct Friction between the wheels and the road is the only horizontal external force acting on the car (if air resistance is negligibEe). Friction not only slows down oars when brakes are applied; it also propels cars
fonivard when they accelerate! The most powerful engine cannot possibly produce an external force on the
car because it is part of the car. Part B
7 Use Newton's laws to ﬁnd an expression for the net external force acting on the car. Ignore air resistance. Express your answer in terms of any given variables and f, the force of friction acting on each wheel. [:1 M Answers Give Up
7 .Masteriiigphysﬁs: Ch 7 HW15  Google ctﬁne ¥ , h—Hl; _ “Lil‘tgﬁn ﬂ httpsz/lsession.mastering physics.com/myct/itemView?assig nmentProbIemID=603836045totfset=next 1 AP Physics 1 Ch 7 HW15 Item 10 Item 10 Figure 1) The car shown in the ﬁgure has mass m
(this includes the mass of the wheels). The wheels
have radius r, mass mw, and moment of inertia
I : kmw1'2 . Assume that the axles apply the same
torque ‘r to all four wheels. For simplicity, also assume
that the weight is distributed uniformly so that all the —of1 < > 'Masteriiigphyuits: Ch 7 HW15 7 Google ctﬁne ; Help l c Resources v « previous l 10 of 15 I next » Part C
Use Newton's laws to ﬁnd an expression for N, the normal force on each wheel. Express your answer in terms of m and g, the magnitude of the acceleration due to gravity. _ 2 I) I m Answers Give Up Correct With this expression for the normal force on each tire we can now examine an interesting sidenote. This
isn't crucial for the remainder of this question, but it is interesting. The coefﬁcient of fricﬁon p, between
rubber and cement is about 0.9. Also, the maximum ﬁ'ictional force is ftmm : pN. Substituting for f and
N in the scalar expression of Newton's second lawFuet : ma gives ((12)max : ‘59 m 8.8 [lit/S2. With
this acceleration, the car wouid go from U to 60 mph in only about 3 seconds! Of course, air resistance
becomes signiﬁcant at higher speeds, so this simple model does not give accurate results. However, many
race car models can accelerate from 0 to 60 mph in about 3.3 seconds. Part D Now assume that the frictional force f is not at its maximum value. What is the relation between the torque 1
applied to each wheel by the axles and the acceleration a of the car? Once you have the exact expression for v , u—H‘! _ ‘Eihlgtgﬁn ﬂ physics.com/myct/itemView?assig nmentProblemID=603836045coffset=next AP Physics 1 2 oh 7 HW15 Item 10 Help l Close Resources v «previous l 10 of15 I next» Item 10 Figure 1) The car shown in the ﬁgure has mass m
(this includes the mass of the wheels). The wheels
have radius 7', mass mw, and moment of inertia
I : kmwr2 . Assume that the axles apply the same
torque ‘r to all four wheels. For simplicity, also assume
that the weight is distributed uniformly so that all the —of1 < > rubber and cement is about 0.9. Also, the maximum frictional force is fmax = pN. Substituting for f and .
N in the scalar expression of Newton's second lawa : ma gives (aZ)mex : pg m 8.8 rig/52. With this acceleration, the car woutd go from 0 to 60 mph in only about 3 seconds! Of course, air resistance becomes signiﬁcant at higher speeds, so this simple model does not give accurate results. However, many race car models can accelerate from 0 to 60 mph in about 3.3 seconds. Part D Now assume that the frictional force f is not at its maximum value. What is the relation between the torque 1
applied to each wheel by the axles and the acceleration a of the car? Once you have the exact expression fo!
the acceleration, make the approximation that the wheels are much lighter than the car as a whole. Express your answer in terms of some or all of the variables m, r, 1 and the magnitude of the
acceleration due to gravity g. g
1711' a [ Hints mAnswers Give Up ReviewFart Correct is this answer believable? ‘l. Certainly, it makes sense that the acceleration is proportional to the torque applied.
2. Aiso, for a given 1' you would expect a lighter car to travel faster. Provide Feedback QMamtﬁgphﬁsm7M5‘$°°9_'9Chr°"!9_ — mun 2w 3
AP Physics 1 20 on 7 HW15 Item 12 «previous i 12 of 15 I next » Help 1 c Item 12 Part A , . , , Determine the a: coordinate of the center of gravity of the three coins.
Three Identlcal corns lie on three corners of a square a. = 12.0 cm on a side. as shown in (Figure 1) . Express your answer to three signiﬁcant ﬁgures and include the appropriate units. mug = 4.00 cm [:J m Answers Give Up Figure1 7 of1 < . >
Correct
y
Part B
0 Determine the y coordinate of the center of gravity of the three coins. Express your answer to three signiﬁcant ﬁgures and include the appropriate units. ycg = 4.00 cm [: M Answers Give Up Correct 0
O
a
H Provide Feedback Co nue EMamzmgPhﬁs=ChTMHuog‘Iwme. — ——: 2w ﬁ physics.com/myct/itemView?assig nmentProbIemID=603837178coffset=next AP Physics 1 20 we 1 Close
W . Item13 «previous i 13 of15 I next» Item 13 Pa” A
What is the net torque on the merrygoround'?
Tom and Jew both pl‘Sh 0" the 280 "1 m—diameter Express your answer to three signiﬁcant ﬁgures and include the appropriate units. merrygoround shown in (Figure 1) . Torn pushes
with a force of 49.5 N and Jerry pushes with a force of33.5 N. 138 N'm
You may want to review (m pages 198  203) . v C] Hints MV—AFISWBTS GiVe UP —R9View Fad
Figure 1 Y a“ < i >
\ 1 Part B
\
\ What is the net torque if Jerry reverses the direction that he pushes by 130 a without changing the magnitude
\ of his force?
0
189 _ Express your answer to three signiﬁcant ﬁgures and include the appropriate units. ‘r = 106 Nvm Hints mAnswers Give Up Review Part U Jerry Correct Provide Feedback swamzmgmschmsemg‘uecmi — mun 2m 3 physics.com/myct/itemView?assig nmentProbIemID=603837265coffset=next AP Physics 1 2015 w i %
en 7 HW15 Item 14
«previous ‘ 14 of 15 I next »
Item 14
Part A In (Figure 1) , force 132 acls half as far from the pivot asﬁl. What magnitude of I32 causes the net torque on the rod to be zero? Express your answer using two signiﬁcant ﬁgures. F2 = 28 N
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