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习题练习:gc textbook chapter 8 Rotational Motion



 作者: admin   总分: 110分  得分: _____________

答题人: 匿名未登录  开始时间: 24年12月27日 14:40  切换到: 整卷模式

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1#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A bicycle odometer (w2w *h;m tztm2qhich measures distance traveled) is attached near the wheel hub and is designed for 27-inch wheels. What happens if you* t2 hwq;2zmtm use it on a bicycle with 24-inch wheels?
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2#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Suppose a disk rotates at constant angular velocity. Does a point o cjasli8c.z ,v+ .,rgbn the rim have radial and/or tangential acceleration? If the disk’s angular velocity increases uniformly, does the point have radial and/or tangential acceleration? For which cases wou8sgj,.l,i+ .arbczc vld the magnitude of either component of linear acceleration change?
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3#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Could a nonrigid body be described by a single value of hfag2q v.o;f6 the angular velocity $\omega$ Explain.
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4#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Can a small force ever exert a greater torque than a larger force? Explm g e1+2ly3khroy 4m+iain.
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5#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
If a force $\vec{F}$ acts on an object such that its lever arm is zero, does it have any effect on the object’s motion? Explain.
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6#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Why is it more difficult to do a sit-up with your handb sas02 uaz6c,0ekbxggv791 ws behind your head than when your arms are stretched out in front of you? A diagram ma6uv7sgb c20b1 g,s 9wxzae0ak y help you to answer this.
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7#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A 21-speed bicycle has 6- h7wv*+ q bh -h;q1 : nyol7fzj(nxcuucwd6xseven sprockets at the rear wheel and three at the pedal cranks. In which gear is it harder to pedal, a small rear sprocket or a large rear sprocket? Why? In which gear is it harder to pedacvxo7qf-j 1-xy6nhhwch:dz u ln *q7;(w6+bul, a small front sprocket or a large front sprocket? Why?
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8#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Mammals that depend on being able to run fast have slender lg* af-rhr q,c53p z;quower legs with flesh and muscle concentrated high, close to the body (Fig. 8–34). On the basis of rotational dynamics, explain why this distribution of macg*q-qap;3zfrh r5 ,uss is advantageous.
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9#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Why do tightrope walkers (Fig. 8–35) carry a long, narrow beam?v*dq gsx190 + ,izrjzs
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10#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
If the net force on a system is zero, is the net torque also zero? If thbgyi9+awa0 /ke net torque on a system isykw9 ai/ag +0b zero, is the net force zero?
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11#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Two inclines have the same height but make divr1w 5ebp:i)7qhi,i41bas gup0uj/ hd**c xyfferent angles with the horizontal. The same steel ball is rolled down1:y4i/qe i0)p ja1,rdc*bvhi u7 h s5 bx*upgw each incline. On which incline will the speed of the ball at the bottom be greater? Explain.
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12#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Two solid spheres simultaneous84jc c8ua -kva.ia 81alec* ewly start rolling (from rest) down an incline. One sphere has twice the radius and twice the mass of the other. Which reaches the bottom of the incline first? Which has i.8 jk- 1ccaw4eeavlca8 a 8u*the greater speed there? Which has the greater total kinetic energy at the bottom?
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13#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A sphere and a cylinder have l nuz eh- 9).np+lcrpxc eic7; s7fj7:the same radius and the same mass. They start from rest at the top of an inh; :.+l7n j9)ep fcsur7 -cx7zplceincline. Which reaches the bottom first? Which has the greater speed at the bottom? Which has the greater total kinetic energy at the bottom? Which has the greater rotational KE?
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14#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
We claim that momentum and angular momentum are cdl n (3z mhdf/,nmfh9tgzs )3;onserved. Yet most moving or rotating objects eventually slow down and sto zt)3(ddmf,; z hshgnl9m/fn3p. Explain.
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15#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
If there were a great migration of people toward the Earth’s equator, how wou nsix)-;qn/rbnyh rn0su 0;(oun8 9bwld this affect the length of r; 9/0-sus0u8nbi(yoh)r nn wq;nbn xthe day?
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16#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Can the diver of Fig. 8–29 do a somergsu7ogi:g5 j : n/gmm+sault without having any initial rotation when s gu5n g:mog m+7:/gjishe leaves the board?
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17#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
The moment of inertia of a rotating solid disk about an axis t-.cbrbv zg*l1f 3)xtrhrough its center of mass-bf3 zgcbrv) l1x.r* t is $\frac{1}{2}WR^2$ (Fig. 8–21c). Suppose instead that the axis of rotation passes through a point on the edge of the disk. Will the moment of inertia be the same, larger, or smaller?
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18#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Suppose you are sitting on a rotating stool holding a 2-kg massla -z )-kkhcp63p femfeuz4,h0 p84jmq3 k2zh in each outstretched hand. If you suddenly drop the masses, will your angular velocity increase, decrease, or stay the s4fphu62 l3pmez- h,kfmp4 zkcke-a)z3 08jhqame? Explain.
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19#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Two spheres look identical and have the same mass. However, one is hollow adp; muckq3 .4hnd the other is solid. Describe an experiment to determine which 4pkhq d3 ;u.cmis which.
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20#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
In whatdirection is the Earth’s angular velocity vector as it rotates daily about itsaxis?
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21#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
The angular velocity of a wheel rotating on a horizon zx;21rqy:d6swmmv(lu7p8 vutal axle points west. In what direction is the linear velocity of a point on the top of the wheel? If the angular acceleration poinwx7m m:6;y2vdrvuz 8q(1p lsuts east, describe the tangential linear acceleration of this point at the top of the wheel. Is the angular speed increasing or decreasing?
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22#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Suppose you are standing on the edge of a large freely rotating)ft oyh( y78)uckm/je turntable. What happens if you walk toward th y ejh7otyfc/)k um8()e center?
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23#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A shortstop may leap into the air to catch a ball and throw it quickly. As he y)-r9i 7z mkmethrows i)e-9 7yrz mmkthe ball, the upper part of his body rotates. If you look quickly you will notice that his hips and legs rotate in the opposite direction (Fig. 8–36). Explain.
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24#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
On the basis of the law1ms4z* np9erxcr9 l 0k of conservation of angular momentum, discuss why a helicopter must 9p 1mx4cr rke*9ln zs0have more than one rotor (or propeller). Discuss one or more ways the second propeller can operate to keep the helicopter stable.
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25#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Express the followings)p 27tnorpux**k je5 angles in radians: (a) 30 $^{\circ} $, (b) 57 $^{\circ} $, (c) 90 $^{\circ} $, (d) 360 $^{\circ} $, and (e) 420 $^{\circ} $. Give as numerical values and as fractions of $\pi$.(Round to two decimal places)
(a)   $rad$ (b)   $rad$ (c)    $rad$ (d)    $rad$ (e)    $rad$

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26#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Eclipses happen on Earth because of an amazing coincidence.e ; y o8s-n2v5f2cswib Calculate, using the information inside the Front Cover, the angular diameters (in radians) of the Sun and tse2 8w 5ioy;cfs2vbn- he Moon, as seen on Earth.
Sun =    $rad$ Moon =    $rad$

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27#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A laser beam is directedwwp nm 4kh.s5xw07pfdj1hoh8,ap,w * at the Moon, 380,000 km from Earth. The beam diverges at an angl ph fww. a*jhsk0n,,o48 p71mhdwxwp5e $\theta$ (Fig. 8–37) of $1.4\times10^{-5}$ rad What diameter spot will it make on the Moon?    m



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28#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The blades in a blender rotate at a rate of 6500 rpm. When the motor is turk x0udu 7-0vtoned off during operation, the blade07vud okt0x- us slow to rest in 3.0 s. What is the angular acceleration as the blades slow down?    $rad/s^2$

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29#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A child rolls a ball on nw0+7p/azl*jrmok3q 9 ine ds 1g1n0i a level floor 3.5 m to another child. If the ball makes 15.0 re1i nis*0pqr 10 l+o/km g9wnznj7eda3volutions, what is its diameter?    m

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30#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bicycle with tires 68 cmq;(3ictb-kyd 3j da c/ in diameter travels 8.0 km. How many revolutions do the whbida;3(cj3 y/kc d -tqeels make?    $rev$

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31#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) A grinding wheel 0.35 m in diameter rotates at 2500 rpm. Calculate pkx1r22xopjmbqob0 wc a:08 h f/.l *xwpp79eits angular vel/ra2:x qbo09xe pw8jmf1pp x 0*c.7pk l 2bwohocity in $rad/s$ $\omega$ =    $rad/sec$
(b) What are the linear speed and acceleration of a point on the edge of the grinding wheel? v =    $m/s$ $a_R$ =    $ m/s^2$

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32#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A rotating merry-go-round makes one complpmmaw o 0ul +csua7b8k-):m8hn- 4ynwete revolution in 4.0 s (Fig. 8–38). (a) Whatc 8k-uml0u:b)wwh8p 7n n y+soa4mm-a is the linear speed of a child seated 1.2 m from the center?    $m/s$
(b) What is her acceleration (give components)?    $m/s^2$    the center

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33#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Calculate the angular velocity of the Earth (a) wkxlame-+ycy9c *i ;ihg. .m. in its orbit around the Sun    $ \times10^{-7 }$ $rad/s$
(b) about its axis.    $ \times10^{-5}$ $rad/s$

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34#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the linear speed of a point wjs94g 4p4* akz6dljt
(a) on the equator,    $m/s$
(b) on the Arctic Circle (latitude 66.5$^{\circ} $ N),    $m/s$
(c) at a latitude of 45.0$^{\circ} $ N, due to the Earth’s rotation?    $m/s$

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35#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How fast (in rpm) must a centrifuge rotate if a particle 7.0 cm from the axis eev3n/ d)jtct:e; e d/of rotation is to experience an acceleration of 10eje )vt/ /de ntd;:ec30,000 $g’s$?    $rpm$

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36#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 70-cm-diameter wheel accelerates uniformly about its cent8h2f9 k vyn3eh 7ctxv5er from 130 rpm to 280 rpm in 4.0f978thy5xe 3 2hckvvn s. Determine
(a) its angular acceleration,$\approx$    $rad/s^2$(Round to one decimal places)
(b) the radial and tangential components of the linear acceleration of a point on the edge of the wheel 2.0 s after it has started accelerating. $a_R$    $m/s^2$ $a_{tan}$    $m/s^2$

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37#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A turntable of radius2d4 r *cm47y)jhtjilj $R_1$ is turned by a circular rubber roller of radius $R_2$ in contact with it at their outer edges. What is the ratio of their angular velocities, $\omega_1$ / $\omega_2$
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38#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  In traveling to the Moon, astronauts aboard the Apollo spacecraft put themselve g((j;/beoom ks into a slow rotation to distribute the Sun’s energy evenly. At the start of their trip, they accelerated from no rotation to 1.0 revolution every minute during a 12-min time interval. The spacecra ( eog/bmj;o(kft can be thought of as a cylinder with a diameter of 8.5 m. Determine
(a) the angular acceleration, $\approx$    $rad/s^2$
(b) the radial and tangential components of the linear acceleration of a point on the skin of the ship 5.0 min after it started this acceleration. $a_{tan}$ =    $ \times10^{ -4}$ $m/s^2$ $a_{rad}$ =    $ \times10^{ -3}$ $m/s^2$

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39#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A centrifuge accelerates uniformly from rest to yk+2l2(mrpul mzu5n ,15,000 rpm in 220 s. Through how many revolutions did ik , uzm(+ll 2yum25rnpt turn in this time?    $rev$

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40#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An automobile engine.(9nb sbf v)sd0jy1.j;fpl rz b)/ngj slows down from 4500 rpm to 1200 rpm in 2.5 s. Calculate
(a) its angular acceleration, assumed constant,    $rad/s^2$
(b) the total number of revolutions the engine makes in this time.    $rev$

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41#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Pilots can be tested for the stresses of f :j5f;h ixd saiozs:2*lying highspeed jets in a whirling “human centrifuge,” whichd:ss*;fa:zii2jx5 h o takes 1.0 min to turn through 20 complete revolutions before reaching its final speed.
(a) What was its angular acceleration (assumed constant),    $rev/min^2$
(b) what was its final angular speed in rpm?    $rpm$

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42#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A wheel 33 cm in diameter accelerates uniformly from 240 rpm to 360 rpm in+ns4 a ym4lho 6 ysf4*1(zmz/cewuv *u 6.5 s. How far will a point on the edge of the wheel have tw4v( +4mclz* n1uhus/fo 6m*4z eyy saraveled in this time?    m

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43#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A cooling fan is turned off when it is running at 850rev/min It 2 mm0j3fx8kwskh+q kr*d2f; gturns 1500 revolutions befm xsmk8gf2wqrd3k *2h+ ;jk0fore it comes to a stop.
(a) What was the fan’s angular acceleration, assumed constant?    $\frac{rad}{s^2}$
(b) How long did it take the fan to come to a complete stop?    s

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44#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The tires of a car make 65 re p5i.x hz 1rf9-kxiv8zvolutions as the car reduces its speed uniformly from1xxz-.k5vhf9zpii8 r 95km/h to 45km/h The tires have a diameter of 0.80 m.
(a) What was the angular acceleration of the tires? $\approx$    $rad/s^2$
(b) If the car continues to decelerate at this rate, how much more time is required for it to stop?    s

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45#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The tires of a car make 65 revolutions as thvpl eg-d/ 5f8ie car reduces its speed uniformly from 9lfv5/d8 pegi -5km/h to 45km/h The tires have a diameter of 0.80 m.
(a) What was the angular acceleration of the tires? $\approx$    $rad/s^2$
(b) If the car continues to decelerate at this rate, how much more time is required for it to stop?    s

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46#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 55-kg person riding a bike puts aab*p, w( dpj u(yuro8)ll her weight on each pedal when climbing a hill. The puo,r( j yb8 a)du*pw(pedals rotate in a circle of radius 17 cm.
(a) What is the maximum torque she exerts?    $m \cdot N$
(b) How could she exert more torque?

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47#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person exerts a force of 55 N on the end of a door -z qj(.by*gxl 74 cm wide. What is the magnitud-.x*zbg(yqj le of the torque if the force is exerted
(a) perpendicular to the door    $m \cdot N$
(b) at a 45 $^{\circ} $ angle to the face of the door?    $m \cdot N$

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48#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Calculate the net torque about the axle of the wheel shown in Fig. 8–39. Aj,xm5t950 +m* ftimh sysxxo)ssume that a fricti5hm+9 mxofjtsx*t msx ,yi)50on torque of 0.4 $m \cdot N$ opposes the motion.    $m \cdot N$  



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49#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
Two blocks, each of mass m, are attached to the endhnvo 6kgm6h:t sq/.rdfx/5;ds of a massless rod which pivots as shown in Fig. 8–40. Initially the rod is held in the horizontal position and then released. Calculate the magnitude and di hh/m6.f/tv6xngqdos:k5r;d rection of the net torque on this system.
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50#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The bolts on the cylinder head of a5t:qhnxbb 5. on engine require tightening to a torque of 38bxq 5 5obhtn.: $m \cdot N$ If a wrench is 28 cm long, what force perpendicular to the wrench must the mechanic exert at its end?    N
If the six-sided bolt head is 15 mm in diameter, estimate the force applied near each of the six points by a socket wrench (Fig. 8–41).    N


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51#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Determine the moment of inertia of a 10.8-kg sphere of radius 0.64kj.s )mxdo1s c9/- fij8 m when the axis of rotation is t i- jm sksoxf.c/)jd19hrough its center.    $kg \cdot m^2$

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52#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Calculate the moment of inertia of a bicycle wheel v- odvt4ikbq k,ep17( 66.7 cm in diameter. The rim and tire have a combined mass of 1.25 kg. The mass od1i7,bk4vvo (tkq- pe f the hub can be ignored (why?).    $kg \cdot m^2$

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53#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A small 650-gram ball on the end of a thin, lightb t,ro d.m6 kyz32.xf 3e2xwhy rod is rotated in a horizontal ciref2 y xtydw z 3.xkho23.,b6mrcle of radius 1.2 m. Calculate
(a) the moment of inertia of the ball about the center of the circle,    $kg \cdot m^2$
(b) the torque needed to keep the ball rotating at constant angular velocity if air resistance exerts a force of 0.020 N on the ball. Ignore the rod’s moment of inertia and air resistance.    $m \cdot N$

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54#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A potter is shaping a bowl on a potteruvv cl;q) hs 0vf(se13 -u *woih47cant 9spb1’s wheel rotating at constant angular speed (Fig. 8–42). The friction force between her hands and h9 qu3 lv)s4( be-ncv7ihpuw11ts*voa0s fc; the clay is 1.5 N total.
(a) How large is her torque on the wheel, if the diameter of the bowl is 12 cm?    $m \cdot N$
(b) How long would it take for the potter’s wheel to stop if the only torque acting on it is due to the potter’s hand? The initial angular velocity of the wheel is 1.6 rev/s, and the moment of inertia of the wheel and the bowl is 0.11 $kg \cdot m^2$.    s

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55#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Calculate the moment of inertia of the array of point obje4 2nf8)jd nhjqcts shown in Fig. 8–43 abq4fdn8 jj)nh2out
(a) the vertical axis,    $kg \cdot m^2$
(b) the horizontal axis. Assume m=1.8 kg,M=3.1kg and the objects are wired together by very light, rigid pieces of wire. The array is rectangular and is split through the middle by the horizontal axis.    $kg \cdot m^2$
(c) About which axis would it be harder to accelerate this array?



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56#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An oxygen molecule consists of two oxygen atoms whosex/ 35jp* ervo rzz2e2z total mass is $5.3 \times10^{ -26}$ kg and whose moment of inertia about an axis perpendicular to the line joining the two atoms, midway between them, is $ 1.9\times10^{-46 }$ $kg \cdot m^2$ From these data, estimate the effective distance between the atoms.    $\times10^{-10 }$ m

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57#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  To get a flat, uniform cylindrical satellite spinning at the correct ct +/57m qvj9hdztb)brate, engineers fire four tangential rockets as shown in Fig. 8–44. If the satelliteb htq9/7dzc)jtvm5 +b has a mass of 3600 kg and a radius of 4.0 m, what is the required steady force of each rocket if the satellite is to reach 32 rpm in 5.0 min? $\approx$    N(round to the nearest integer)


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58#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A grinding wheel is a uniform cylinder with a radius of 8.50 cm and .a,5e u 53ze hwysgxj0a mass of 0.580 kg. Cale 5yx 5g.uwea0sj,z3hculate
(a) its moment of inertia about its center, $\approx$    $kg \cdot m^2$
(b) the applied torque needed to accelerate it from rest to 1500 rpm in 5.00 s if it is known to slow down from 1500 rpm to rest in 55.0 s。    $m \cdot N$

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59#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A softball player swin;,7usl g7uk me)1pnj g *lh4jfm8r d8qgs a bat, accelerating it from rest to 3 $rev/s$ in a time of 0.20 s. Approximate the bat as a 2.2-kg uniform rod of length 0.95 m, and compute the torque the player applies to one end of it.    $m \cdot N$

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60#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A teenager pushes tangentially on a small hand-driven bbqj o50v lwny/;-zs2 merry-go-round and is able to accelerate it from rest to a frequency of 15 rpm in 10.0 s. Assume the merry-go-round is a uniform disk of radius 2.5 m and has a mass of 760 kg, and two children (each with a mass of 25 kg) sit opposite each other on tnl s/-zb 5b o0wqvyj2;he edge. Calculate the torque required to produce the acceleration, neglecting frictional torque. $\approx$   $m \cdot N$ What force is required at the edge?    N

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61#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A centrifuge rotor rotating at 10,300 rpm is shut off and is even42mrts7p;a fy tually brought uniformly to rest by a frictional torque f7 m rts2p4ya;of 1.2 $m \cdot N$ If the mass of the rotor is 4.80 kg and it can be approximated as a solid cylinder of radius 0.0710 m, through how many revolutions will the rotor turn before coming to rest,    $rev$ how long will it take?    s

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62#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The forearm in Fig. 8–45 accelerc 1 5fhl4b-6ztw no0vkates a 3.6-kg ball at 7 $m/s^2$ by means of the triceps muscle, as shown. Calculate
(a) the torque needed,    $m \cdot N$
(b) the force that must be exerted by the triceps muscle. Ignore the mass of the arm.    N


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63#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Assume that a 1.00-kg ball is thrown solely by the actiqb p*sue .rmc ygx6k, h-;*r*won of the forearm, which rotates about the elbow joint under the action of the triceps muscubrre-ymq ch* *; w6p.xs*,gkle, Fig. 8–45. The ball is accelerated uniformly from rest to 10 $m/s$ in 0.350 s, at which point it is released. Calculate
(a) the angular acceleration of the arm,    $rad/s^2$
(b) the force required of the triceps muscle. Assume that the forearm has a mass of 3.70 kg and rotates like a uniform rod about an axis at its end.    N



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64#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A helicopter rotor blade can be considered a lols to0 qx2s*e2ng thin rod, as shown in Fig. 8–46. * ox02ssel2qt
(a) If each of the three rotor helicopter blades is 3.75 m long and has a mass of 160 kg, calculate the moment of inertia of the three rotor blades about the axis of rotation.    $kg \cdot m^2$
(b) How much torque must the motor apply to bring the blades up to a speed of 5 $rev/s$ in 8.0 s?    $m \cdot N$


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65#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
An Atwood’s machine co tt2tu xom3i*9nsists of two masses, $m_1$ and $m_2$ which are connected by a massless inelastic cord that passes over a pulley, Fig. 8–47. If the pulley has radius R and moment of inertia I about its axle, determine the acceleration of the masses $m_1$ and $m_2$ and compare to the situation in which the moment of inertia of the pulley is ignored. [Hint: The tensions $F_{T1}$ and $F_{T2}$ are not equal. We discussed this situation in Example 4–13, assuming for the pulley.]

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66#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A hammer thrower accelerw.iwlrzs 6ddf+cn;i a 4 +*t,kates the hammer from rest within four full turns (revolutions) and relea+a*i.n+ w;r lkzfwctsid4 6 d,ses it at a speed of 28 $m/s$ Assuming a uniform rate of increase in angular velocity and a horizontal circular path of radius 1.20 m, calculate
(a) the angular acceleration,    $rad/s^2$
(b) the (linear) tangential acceleration,    $m/s^2$
(c) the centripetal acceleration just before release,    $m/s^2$
(d) the net force being exerted on the hammer by the athlete just before release,    N
(e) the angle of this force with respect to the radius of the circular motion.    $^{\circ} $

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67#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A centrifuge rotor has a mh9p5 d/iyyj. .h/o:zq1c fausj:zr1 t oment of inertia of $3.75 \times10^{-2 }$ $kg \cdot m^2$ How much energy is required to bring it from rest to 8250 rpm?    J

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68#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An automobile engine develops a torq cm fy5mh/-n, (bzw3ueue of 280 $m \cdot N$ at 3800 rpm. What is the power in watts and in horsepower?    W    hp

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69#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bowling ball of mass 7.3 k ouceex+rj7ok4 ww0 +5g and radius 9.0 cm rolls without slipping down a lan7oe jxoce45+w r0w+kue at 3.3 $m/s$ Calculate its total kinetic energy.    J

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70#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Estimate the kinetic energy of the Eart 8 etfp2gesv*:/4ijvlh with respect to the Sun as the sum of two v s82pf v4j*i:get/ elterms,
(a) that due to its daily rotation about its axis,$KE_{daily}$=    $\times10^{29 }$ J
(b) that due to its yearly revolution about the Sun. $KE_{yearly}$+    $\times10^{33 }$ J [Assume the Earth is a uniform sphere with $6 \times10^{ 24}$ kg and $6.4 \times10^{6 }$ m and is $1.5 \times10^{8 }$ km from the Sun.]$KE_{daily}$ + $KE_{yearly}$ =    $ \times10^{33 }$ J

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71#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A merry-go-round has a mass of 1640 kg and a radius oz :gfqub0n9 *vz )r,tqf 7.50 m. How much net work is requiredz0 )fuqr,vb*t:9g nqz to accelerate it from rest to a rotation rate of 1.00 revolution per 8.00 s? Assume it is a solid cylinder.    J

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72#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A sphere of radius 20.0 cm and mass 1.80 kg startsv7m1 lj 6zzoa:t qi5g2 from rest and rolls without svmj7:qi1az6 2l5 zotglipping down a 30.0 $^{\circ} $ incline that is 10.0 m long.
(a) Calculate its translational and rotational speeds when it reaches the bottom. $v_{CM}$ =    $\omega$ =    $rad/s$
(b) What is the ratio of translational to rotational KE at the bottom?    Avoid putting in numbers until the end so you can answer:
(c) do your answers in (a) and (b) depend on the radius of the sphere or its mass?

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73#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two masses, $m_1$ = 18 kg and $m_2$ = 26.5 kg are connected by a rope that hangs over a pulley (as in Fig. 8–47). The pulley is a uniform cylinder of radius 0.260 m and mass 7.50 kg. Initially, is on the ground and $m_2$ rests 3.00 m above the ground. If the system is now released, use conservation of energy to determine the speed of $m_2$ just before it strikes the ground. Assume the pulley is frictionless.    $m/s$


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74#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 2.30-m-long pole is balanced vertically on its tip. It startspq/8 x7q zt7ql to fall and its lower end does not slip. What will be the speed of the upper end of the pole just before it hits th8ltq7zq/7q x pe ground? [Hint: Use conservation of energy.]    $m/s$

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75#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the angular momentum of a 0.210xw ,,xx4m ab6t-kg ball rotating on the end of a thin string in a circle of radius 1.10 m at an angularxw ,abxmt,64x speed of 10.4 $rad/s$?    $kg \cdot m^2$

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76#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) What is the angular momentum of a 2.8-kg uniform cylindrical gri*rb ac fnr hs;-.td-g+nding wheel of radius 18 cm when rotating at 1500t-ar*hdc s bf+.r;-ng rpm?    $kg \cdot m^2$
(b) How much torque is required to stop it in 6.0 s?    $m \cdot N$

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77#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A person stands, hands at his side, onerqp- hstlsy xu.,o5p;1+ 1vi a platform that is rotating at a rate of 1.3rev/s Itipr1+vx1 h5s q ;ls-eo,u py.f he raises his arms to a horizontal position, Fig. 8–48, the speed of rotation decreases to 0.8 $rev/s$ (a) Why?
(b) By what factor has his moment of inertia changed?

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78#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A diver (such as the one s;1zn08mlpb(2o fqu adgbw d (q*n:mi3hown in Fig. 8–29) can reduce her moment of inertia by a factor of about 3.5 when changing f b:*q0doiql(1 um ;8 fbn (gwnzdap32mrom the straight position to the tuck position. If she makes 2.0 rotations in 1.5 s when in the tuck position, what is her angular speed ($rev/s$) when in the straight position?   $rev/s$


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79#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A figure skater can increh+ px py4xp gb)zz4*m j47pe*qase her spin rotation rate from an initial rate of 1.0 rev every 2.0 s to a final ratzxm)44xqhz*bj*p+g pey 7p 4pe of 3 $rev/s$ If her initial moment of inertia was 4.6 kg*$m^2$ what is her final moment of inertia? How does she physically accomplish this change?    $kg \cdot m^2$

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80#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A potter’s wheel is rotating around a vertical axis through its center at0c) vc:*sp a qe0hmkkw iq*0)p a frequency of 1.5rev/s The wheel can be considered a uniform disk of mass 5.0 kg and diameter 0.40 m. The potter then throws a 3.1-kg chunk of clay, approximately shaped as a f) 0*c kqa)qcev0sw*ihk0m p: plat disk of radius 8.0 cm, onto the center of the rotating wheel. What is the frequency of the wheel after the clay sticks to it?    $rev/s$

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81#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) What is the angular momentum of a figure skater spinning at h) .ox-v g 1dnj,4 ) hin6j:v+xmyhses3.5 $rev/s$ with arms in close to her body, assuming her to be a uniform cylinder with a height of 1.5 m, a radius of 15 cm, and a mass of 55 kg?    $kg \cdot m^2$
(b) How much torque is required to slow her to a stop in 5.0 s, assuming she does not move her arms?    $m \cdot N$

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82#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Determine the angular mom b7:nrgyl 1g6lc vb7t6xtk* 9dentum of the Earth
(a) about its rotation axis (assume the Earth is a uniform sphere),    $\times 10^{33} \; kg \cdot m^2$

(b) in its orbit around the Sun (treat the Earth as a particle orbiting the Sun). The Earth has mass $6 \times 10^{24} \; kg$ and radius $6.4 \times 10^{6} \; m$ and is $1.5 \times 10^{8} \; km$ from the Sun.    $\times10^{40} \; kg \cdot m^2$

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83#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A nonrotating cylindrical disk of moment of ineroud1)ii 0 2zcrp1hwm) tia I is dropped onto an identical disk rotating at angulahp z)1wo0diiruc )2 m1r speed $\omega$ Assuming no external torques, what is the final common angular speed of the two disks?
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84#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A uniform disk turns at 2.4: -mjlqn 44ohq $rev/s$ around a frictionless spindle. A nonrotating rod, of the same mass as the disk and length equal to the disk’s diameter, is dropped onto the freely spinning disk, Fig. 8–49. They then both turn around the spindle with their centers superposed. What is the angular frequency in rev/s of the combination?    $rev/s$


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85#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A person of mass 75 kg stands at the center of a ro* hz*6.c.s kpt-v nztutating merry-go-round platform of radius 3.0 m and moment of ic* t6z. uhkvpntz.*s -nertia 920 $kg \cdot m^2$ The platform rotates without friction with angular velocity 2 $rad/s$ The person walks radially to the edge of the platform.
(a) Calculate the angular velocity when the person reaches the edge.    $rad/s$
(b) Calculate the rotational kinetic energy of the system of platform plus person before and after the person’s walk.$KE_i$ =    J $KE_f$ =    J

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86#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 4.2-m-diameter merry-go-round is rotating freely with an angular velob g2o2f4 ;isy +p ac y)6oe2k1vd6,jxudde8mncity of 0. jimpas 61e,xdf yuyg26co+v ke84;do2)dn2 b8 $rad/s$ Its total moment of inertia is 1760 $kg \cdot m^2$ Four people standing on the ground, each of mass 65 kg, suddenly step onto the edge of the merry-go-round. What is the angular velocity of the merry-go-round now?    $rad/s$ What if the people were on it initially and then jumped off in a radial direction (relative to the merry-go-round)?    $rad/s$

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87#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Suppose our Sun eventually collapses into a white dwarf, losing about half,6culv4 s6ty+xr(m k:hg h8b v its mass ,64urvy(b6 + vmt:gh chlsx8kin the process, and winding up with a radius 1.0% of its existing radius. Assuming the lost mass carries away no angular momentum, what would the Sun’s new rotation rate be?(round to the nearest integer)$\approx$    $rad/s$ (Take the Sun’s current period to be about 30 days.) What would be its final KE in terms of its initial KE of today?$KE_{f}$=    $KE_{i}$

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88#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Hurricanes can involve windk63doy,mugs9 gocseedp ;43 ,s in excess of 120 $km/h$ at the outer edge. Make a crude estimate of
(a) the energy,    $ \times10^{16 }$ J
(b) the angular momentum, of such a hurricane, approximating it as a rigidly rotating uniform cylinder of air (density 1.3 $kg \cdot m^2$) of radius 100 km and height 4.0 km.    $ \times10^{20 }$ $kg \cdot m^2$

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89#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An asteroid of mass ny:cx7k 0-m yg$ 1.0\times10^{ 5}$ traveling at a speed of relative to the Earth, hits the Earth at the equator tangentially, and in the direction of Earth’s rotation. Use angular momentum to estimate the percent change in the angular speed of the Earth as a result of the collision.    $\times10^{-16 }$ %

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90#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A person stands on a platform, initially at rest, thaywm y6sa: h.7ct can rotate freely without friction. The moment of inertia of the person plus the plch.:maws 6y 7yatform is $I_P$ The person holds a spinning bicycle wheel with its axis horizontal. The wheel has moment of inertia $I_W$ and angular velocity $\omega_W$ What will be the angular velocity $\omega_W$ of the platform if the person moves the axis of the wheel so that it points (a) vertically upward, (b) at a 60º angle to the vertical, (c) vertically downward? (d) What will $\omega_P$ be if the person reaches up and stops the wheel in part (a)?
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91#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Suppose a 55-kg person stands at the edge of a 6.5q1da 2;c 5s ,c cl(oc9:ldnppx-m diameter merry-go-round turntable that is mounted on frictionless bearings and has a moment of inertia cldn9 c soqp c:ap2c(51;l dx,of 1700 $kg \cdot m^2$ The turntable is at rest initially, but when the person begins running at a speed of 3.8 $m/s$ (with respect to the turntable) around its edge, the turntable begins to rotate in the opposite direction. Calculate the angular velocity of the turntable.    $rad/s$

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92#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A large spool of rope rolls on the ground with the end of t3)f 0iej9bmqyctc,z)-nh- :ji3fcv ehe rope lying on the top edge of the spool. A person grabs the end of the rope and walks a distance L, holding onto itcme3t:cy-jn e0zb h -3 j,)f9 qfvic)i, Fig. 8–50. The spool rolls behind the person without slipping. What length of rope unwinds from the spool? How far does the spool’s center of mass move?
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93#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The Moon orbits the Earth such that the same side always faces the Earth. D3 tdv m..c8h m/vpkt4cz(5fkb5chq3 l etermine the ratio of the Moon’s spin angular momentum (about its own axis) to its orbital angular momentum. (In the latter case, treat the Moon as a particle orbitk..hb k58h c5fldzpmtq34ct/vcm( 3 ving the Earth.)    $\times10^{ -6}$

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94#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A cyclist accelerates from rest at a rai3h wftlo0x qmao(ohx y53 36*te of 1 m/$s^2$ How fast will a point on the rim of the tire at the top be moving after 3.0 s? [Hint: At any moment, the lowest point on the tire is in contact with the ground and is at rest — see Fig. 8–51.]    $m/s$


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95#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 1.4-kg grindstone in the shape ola6n oln:;fom/nu q*0f a uniform cylinder of radius 0.20 m acquires a rotational rate of from rest over a 6.0-s interval at constant angular acceleration. Calculate the torque delivered by the *au /;llmn6o o:nq0nf motor.    $m \cdot N$

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96#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) A yo-yo is made of two solid cylindrical disks, each of massg1)l.1n8fwvn gu icy( 0.050 kg and diameter 0.075 m, joined by a (concentric) thin solid cylindrical hub of mass 0.0050 kg and diameter 0.010 m. Use conservation of energy (wgc n1i.)l g8 v1fnuyto calculate the linear speed of the yo-yo when it reaches the end of its 1.0-m-long string, if it is released from rest.    $m/s$
(b) What fraction of its kinetic energy is rotational?    %

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97#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  (a) For a bicycle, how is the angular specjdq5t we ;; bb-)fi/eed of the rear wheel ($\omega_R$) related to that of the pedals and front sprocket ($\omega_F$) Fig. 8–52? That is, derive a formula for ($\omega_R$)/($\omega_F$) Let $N_F$ and $N_R$ be the number of teeth on the front and rear sprockets, respectively. The teeth are spaced equally on all sprockets so that the chain meshes properly.
(b) Evaluate the ratio ($\omega_R$)/($\omega_F$) when the front and rear sprockets have 52 and 13 teeth, respectively,   
(c) when they have 42 and 28 teeth.   


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98#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Suppose a star the size of our Sun, but with mass 8.0 t,yb(u2svj f l+imes as great, were rotating at a speed of 1.0 revolution every 12 days. If it were to undergo gravitational collapse to a neutron star of radius 11 km, losing three-quarters of its mass in the process, what would its rotation speed be? Assume that the star is a uniform sphere at all times, and that theyujs,+b vl2 (f lost mass carries off no angular momentum.    $\times10^{9 }$ $rev/day$

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99#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  One possibility for a low-pollution automobil 9d*gilutn1:+aqv( tze is for it to use energy stored in a heavy rotating flywheel. Suppose such a car has a total mass of 1400 kg, uses a uniform cylindrical flywheel of diametzln *+(ua:gd t 9ivtq1er 1.50 m and mass 240 kg, and should be able to travel 350 km without needing a flywheel “spinup.”
(a) Make reasonable assumptions (average frictional retarding force = 450N twenty acceleration periods from rest to equal uphill and downhill, and that energy can be put back into the flywheel as the car goes downhill), and show that the total energy needed to be stored in the flywheel is about $ 1.7\times10^{8 }$J.    $ \times10^{ 8}$ J
(b) What is the angular velocity of the flywheel when it has a full “energy charge”?    $rad/s$
(c) About how long would it take a 150-hp motor to give the flywheel a full energy charge before a trip? $\approx$    min

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100#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Figure 8–53 illustrates p 2m; 4rcugp olixx5qp/)key8,6 m(xnan $H_2O$ molecule. The O–H bond length is 0.96 nm and the H–O–H bonds make an angle of 104 $^{\circ} $. Calculate the moment of inertia for the $H_2O$ molecule about an axis passing through the center of the oxygen atom
(a) perpendicular to the plane of the molecule,    $\times10^{-45 }$ $kg \cdot m^2$
(b) in the plane of the molecule, bisecting the H–O–H bonds.    $ \times10^{-45 }$ $kg \cdot m^2$


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101#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A hollow cylinder (hoop) is rolling on a horizontal surface at speed v=3.k sa;0kp,e-9rd6 e pxa3 $m/s$ when it reaches a 15 $^{\circ} $ incline.
(a) How far up the incline will it go? $\approx$    m (round to one decimal place)
(b) How long will it be on the incline before it arrives back at the bottom?    s

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102#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A uniform rod of mass M and length L can pivota(pip -a1p9yt freely (i.e., we ignore friction) about a hinge attached to a wall, as in Fig. 8–54. The rod is held horizontally and then released. At the moment of release, determine (a) the angular acceleration of the rod, and (b) the linear acceleration of the tip of the rod. Assume that the force of gravity acts aip a(p yp91ta-t the center of mass of the rod, as shown. [Hint: See Fig. 8–21g.]

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103#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
A wheel of mass M has radius R. It is standi(dqqx j-j1apx)y vw62ng vertically on the floor, and we want to exert a horizontal force F at its axle so that it will climb a step against which it rests (Fixj)xpd2a y6 jq(wvq-1g. 8–55). The step has height h, where h

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104#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A bicyclist traveling with y7vf* n 8 o,/lyz/hqihspeed v=4.2m/s on a flat road is making a turn with a radius The forces acting on the cyclist and cycle are the normal/iz8 ,yq7hy vhl n/f*o force $\left(\mathbf{\vec{F}}_{\mathrm{N}}\right)$ and friction force $\left(\mathbf{\vec{F}}_{\mathbf{fr}}\right)$ exerted by the road on the tires, and $m\vec{\mathbf{g}}$ the total weight of the cyclist and cycle (see Fig. 8–56).
(a) Explain carefully why the angle $\theta$ the bicycle makes with the vertical (Fig. 8–56) must be given by tan $\tan\theta=F_{\mathrm{fr}}/F_{\mathrm{N}}$ if the cyclist is to maintain balance.(round to the nearest integer)
(b) Calculate $\theta$ for the values given.    $^{\circ} $
(c) If the coefficient of static friction between tires and road is $\mu_s=0.70$ what is the minimum turning radius?    m



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105#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Suppose David puts a 0.50-kg rock into a slings (wf+)3 w qeuy,v6c(qfztg+b of length 1.5 m and begins whirling the rock in a nearly horizontal circle above his head, accelerating it from rest to a rate of 120 rpm after 5.0 s. What is the torque required to achieve this feat+ qc6ueft+sw,y v3 )q (wzfgb(, and where does the torque come from?    $m \cdot N$

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106#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Model a figure skater’s body as a solid cylinder and her arms as thin rods, k l,c )ib2rfx1making reasonable estimati,xfbk 2)lc1 res for the dimensions. Then calculate the ratio of the angular speeds for a spinning skater with outstretched arms, and with arms held tightly against her body.   

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107#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You are designing a clutch assembly which consists of two cylis8j2y-zx cz6) dtz :ucndrical plates, of mass sdz:- ut2czczj)6xy8 $M_{\mathrm{A}}=6.0$ $\mathrm{kg}$ and $M_{\mathrm{B}}=9.0$ $\mathrm{kg}$ with equal radii R=0.60 $\mathrm{m}$ They are initially separated (Fig. 8–57). Plate $M_{\mathrm{A}}$ is accelerated from rest to an angular velocity $\omega_1=7.2$ $\mathrm{rad/s}$ in time $\Delta t=2.0$ s Calculate
(a) the angular momentum of $M_{\mathrm{A}}$    $kg \cdot m^2$
(b) the torque required to have accelerated $M_{\mathrm{A}}$ from rest to $\omega_{1}$    $m \cdot N$
(c) Plate $M_{\mathrm{B}}$ initially at rest but free to rotate without friction, is allowed to fall vertically (or pushed by a spring), so it is in firm contact with plate $M_{\mathrm{A}}$ (their contact surfaces are high-friction). Before contact, $M_{\mathrm{A}}$ was rotating at constant $\omega_{1}$ After contact, at what constant angular velocity $\omega_{s}$ do the two plates rotate?    $rad/s$


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108#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A marble of mass m and r- hv3y jwc h0kl52pi z2cer w19fo8/taadius r rolls along the looped rough track of Fig. 8–58. What is the minimum value of the vertical height h that the marble must drop if it is to reach the highest point of the loop without leavw2 fejowp3 hlhcct 02i8-rk59/z ay1ving the track? Assume $r\ll R$ and ignore frictional losses. h =    R



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109#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Repeat Problem 84, but do not a9x,-fkp ( 5u lsqaxk+vssume $r\ll R$ h =    (R-r)

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110#
 
填空题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The tires of a car makew4scg pl c6o-2 85 revolutions as the car reduces its speed uniformly from 90km/h to 60km/h The tires have a diamw g cpsl2co-64eter of 0.90 m. (a) What was the angular acceleration of each tire? $\approx$    $rad/s^2$(round to two decimal place)
(b) If the car continues to decelerate at this rate, how much more time is required for it to stop?    s

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