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习题练习:2011 美国F=ma物理竞赛 F=ma physics competition



 作者: admin   总分: 25分  得分: _____________

答题人: 匿名未登录  开始时间: 23年12月09日 21:14  切换到: 整卷模式

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1#
 
单选题 ( 1.0 分) (组内1/1) 切至整卷模式 搜藏此题  
第 1 题组 (共 1 题 1 分)
  A cyclist travels at a consta:;p6ric)r qr uj6vgr1nt speed of $22.0 \mathrm{~km} / \mathrm{hr}$ except for a 20 minute stop. The cyclists average speed was $17.5 \mathrm{~km} / \mathrm{hr}$. How far did the cyclist travel?

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2#
 
单选题 ( 1.0 分) (组内1/3) 切至整卷模式 搜藏此题  
第 2 题组 (共 3 题 3 分) 当前第1/3题
题组内容描述:
Questions 1 to 3 refer to the three graphs below which show velocity of three objects as a function of time. Each object is moving only in one dimension.
  Rank the magnitudes of the average acceleration during the ten;xyw b3,;gug c65 wgqc second interval.

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3#
 
单选题 ( 1.0 分) (组内2/3) 切至整卷模式 搜藏此题  
第 2 题组 (共 3 题 3 分) 当前第2/3题
题组内容描述:
Questions 1 to 3 refer to the three graphs below which show velocity of three objects as a function of time. Each object is moving only in one dimension.
  Rank the magnitudes of the maximum velocity achieved during the ten sech sukf gc4 .6f8w6v:0bc. izmxond interva8.x:04bwg fc z.6 h6fum viskcl.

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4#
 
单选题 ( 1.0 分) (组内3/3) 切至整卷模式 搜藏此题  
第 2 题组 (共 3 题 3 分) 当前第3/3题
题组内容描述:
Questions 1 to 3 refer to the three graphs below which show velocity of three objects as a function of time. Each object is moving only in one dimension.
  Rank the magnitudes of the distance travel4ge sy g5me 9c/)btod5ed during the ten second interval.

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5#
 
单选题 ( 1.0 分) (组内1/11) 切至整卷模式 搜藏此题  
第 3 题组 (共 11 题 11 分)
  A crude approximation is that the Earth travels :p;tuhlw k.kl 9fe.1c 5is(gdin a circular orbit about the Sun at constant spe1kgck 9ef(ld;:ip5 l.wt us .hed, at a distance of $150,000,000 \mathrm{~km}$ from the Sun. Which of the following is the closest for the acceleration of the Earth in this orbit?

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6#
 
单选题 ( 1.0 分) (组内2/11) 切至整卷模式 搜藏此题  
  A child is sliding out of control with velsvnt+5knm +l1kee 1m8ocity $v_{\mathrm{c}}$ across a frozen lake. He runs head-on into another child, initially at rest, with 3 times the mass of the first child, who holds on so that the two now slide together. What is the velocity of the couple after the collision?

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7#
 
单选题 ( 1.0 分) (组内3/11) 切至整卷模式 搜藏此题  
  An ice skater can rotate about a vertical axis with an angular vk 6vki m/wffv2mi)n,bkd- :df c8xa+ )elocity $\omega_{0}$ by holding her arms straight out. She can then pull in her arms close to her body so that her angular velocity changes to $2 \omega_{0}$, without the application of any external torque. What is the ratio of her final rotational kinetic energy to her initial rotational kinetic energy?

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8#
 
单选题 ( 1.0 分) (组内4/11) 切至整卷模式 搜藏此题  
  When a block of wood with ojvb7 5 8ezh *7qogyc2vc0,0ic6etqc a weight of $30 \mathrm{~N}$ is completely submerged under water the buoyant force on the block of wood from the water is $50 \mathrm{~N}$. When the block is released it floats at the
surface. What fraction of the block will then be visible above the surface of the water when the block is floating?

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9#
 
单选题 ( 1.0 分) (组内5/11) 切至整卷模式 搜藏此题  
  A spring has an equiln(fw h jh/dd+w7 x:.jjibrium length of 2.0 meters and a spring constant of 10 newtons/meter. Alice is pulling on one end of the spring with a force of +7djnw: dhh fw.jx(/j3.0 newtons. Bob is pulling on the opposite end of the spring with a force of 3.0 newtons, in the opposite direction. What is the resulting length of the spring?

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10#
 
单选题 ( 1.0 分) (组内6/11) 切至整卷模式 搜藏此题  
  Which of the following changes will res /tak 5i5gu7e oc)1sf-(tvbae ult in an increase in the period of a simple p)17t (/sief vu boe-5acg5aktendulum?

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11#
 
单选题 ( 1.0 分) (组内7/11) 切至整卷模式 搜藏此题  
  A large metal cylind vx-(x5pd+6aavkr:ym m* i4j (kbwv-trical cup floats in a rectangular tub half-filled with water. The tap is placed over the cup and turned on, releasing water at a constant rate. Eventually the cup sinks to the bottom and is completely submerged. Which of the following five graphs could represent the water level in-:+jr( -pxwtvmvy b a dm(ikax46kv5* the sink as a function of time?


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12#
 
单选题 ( 1.0 分) (组内8/11) 切至整卷模式 搜藏此题  
  You are given a large colry:kj)0 p2pg63 zwvue lection of identical heavy balls and lightweight rods. When two balls are placed at the ends of one rp zpyjr2 v)u 360w:kgeod and interact through their mutual gravitational attraction (as is shown on the left), the compressive force in the rod is $F$. Next, three balls and three rods are placed at the vertexes and edges of an equilateral triangle (as is shown on the right). What is the compressive force in each rod in the latter case?




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13#
 
单选题 ( 1.0 分) (组内9/11) 切至整卷模式 搜藏此题  
  The apparatus in the diagram consists of a solid cylinder n g xmz,.l;wr6yh l ha:+xa86lr8qwg-of radius $1 \mathrm{~cm}$ attached at the center to two disks of radius $2 \mathrm{~cm}$. It is placed on a surface where it can roll, but will not slip. A thread is wound around the central cylinder. When the thread is pulled at the angle $\theta=90^{\circ}$ to the horizontal (directly up), the apparatus rolls to the right. Which below is the largest value of $\theta$ for which it will not roll to the right when pulling on the thread?




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14#
 
单选题 ( 1.0 分) (组内10/11) 切至整卷模式 搜藏此题  
  You have 5 different strings wit 0m7ovr4vxly1i ch .-th weights tied at various point, all hanging from the ceiling, and reaching down to the floor. The string is released at the top, allowing the weights to fall. Which one will create a regular, uniform beating sound as thy 4hv-.mr i70x1lcv ote weights hit the floor?


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15#
 
单选题 ( 1.0 分) (组内11/11) 切至整卷模式 搜藏此题  
  A vertical mass-spring oscillator is displaced ) a5bl*s e(h)n2t7 sfcohfg+j$2.0 \mathrm{~cm}$ from equilibrium. The $100 \mathrm{~g}$ mass passes through the equilibrium point with a speed of $0.75 \mathrm{~m} / \mathrm{s}$. What is the spring constant of the spring?

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16#
 
单选题 ( 1.0 分) (组内1/2) 切至整卷模式 搜藏此题  
第 4 题组 (共 2 题 2 分)
题组内容描述:
Questions 1 and 2 refer to the information and diagram below.Jonathan is using a rope to lift a box with Becky in it; the box is hanging off the side of a bridge, Jonathan is on top. A rope is hooked up from the box and passes a fixed railing; Jonathan holds the box up by pressing the rope against the railing with a massless, frictionless physics textbook. The static friction coefficient between the rope and railing is $\mu_{s}$; the kinetic friction coefficient between the rope and railing is $\mu_{k}<\mu_{s}$; the mass of the box and Becky combined is $M$; and the initial height of the bottom of the box above the ground is $h$. Assume a massless rope.
  What magnitude force does Jonathan need to exert on the0ove0 gl) df :sgr.+,sn:f5dri tsjc1 physics book to keep the rope from slippi0,1)+se .frd:cnviofd0l gs jtr:5gsng?

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17#
 
单选题 ( 1.0 分) (组内2/2) 切至整卷模式 搜藏此题  
  Jonathan applies a normal forcex9p0 ,w p6vqihb( nh1e that is just enough to keep the rope from slipping. Becky makes a small jump, barely leaving contact with the floor of the box. Upon landing on the box, the force of the impact causes the rope to start slipping from Jonathans hand. At what speed does th x(bp whe,hv9i6np10qe box smash into the ground? Assume Jonathans normal force does not change.

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18#
 
单选题 ( 1.0 分) (组内1/1) 切至整卷模式 搜藏此题  
第 5 题组 (共 1 题 1 分)
  A block of mass $m=3.0 \mathrm{~kg}$ slides down one ramp, and then up a second ramp. The coefficient of kinetic friction between the block and each ramp is $\mu_{\mathrm{k}}=0.40$. The block begins at a height $\mathrm{h}_{1}=1.0 \mathrm{~m}$ above the horizontal. Both ramps are at a $30^{\circ}$ incline above the horizontal. To what height above the horizontal does the block rise on the second ramp?

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19#
 
单选题 ( 1.0 分) (组内1/2) 切至整卷模式 搜藏此题  
第 6 题组 (共 2 题 2 分)
题组内容描述:
Questions 1 and 2 refer to the following information
A particle of mass $2.00 \mathrm{~kg}$ moves under a force given by
$$\vec{F}=-(8.00 \mathrm{~N} / \mathrm{m})(x \hat{i}+y \hat{j})$$
where $\hat{i}$ and $\hat{j}$ are unit vectors in the $x$ and $y$ directions. The partricle is placed at the origin with an initial velocity of $\vec{v}=(3.00 \mathrm{~m} / \mathrm{s}) \hat{i}+(4.00 \mathrm{~m} / \mathrm{s}) \hat{j}$.
  After how much time will the particle first return to the 5mcqo/l w2 tm5rouc -/origin?

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20#
 
单选题 ( 1.0 分) (组内2/2) 切至整卷模式 搜藏此题  
  What is the maximum distance5ju3-ln w 2t 8yi7bwxa between the particle and the origin?

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21#
 
单选题 ( 1.0 分) (组内1/5) 切至整卷模式 搜藏此题  
第 7 题组 (共 5 题 5 分)
  An engineer is given a fixed o 3 0as ldym2ez+0pft.volume $V_{m}$ of metal with which to construct a spherical pressure vessel. Interestingly, assuming the vessel has thin walls and is always pressurized to near its bursting point, the amount of gas the vessel can contain, $n$ (measured in moles), does not depend on the radius $r$ of the vessel; instead it depends only on $V_{m}$ (measured in $\mathrm{m}^{3}$ ), the temperature $T$ (measured in $\mathrm{K}$ ), the ideal gas constant $R$ (measured in $\mathrm{J} /(\mathrm{K} \cdot \mathrm{mol})$ ), and the
tensile strength of the metal $\sigma$ (measured in $\mathrm{N} / \mathrm{m}^{2}$ ). Which of the following gives $n$ in terms of these parameters?

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22#
 
单选题 ( 1.0 分) (组内2/5) 切至整卷模式 搜藏此题  
  This graph depicts the tvqjnq;lb5r *+kjypj;e 2 9-tuorque output of a hypothetical gasoline engine as a function of rotation frequency. The engine is incapable of running outside of the graphed range.qn t;jrypub5 *ve+ k;9-2jlj q


At what engine RPM (revolutions per minute) does the engine produce maximum power?

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23#
 
单选题 ( 1.0 分) (组内3/5) 切至整卷模式 搜藏此题  
  A particle is launched from the surface of a uniform, station 4-(yn(4go dt rrvc9xeary spherical planet at d49 4ec otrr-n(ygxv( an angle to the vertical. The particle travels in the absence of air resistance and eventually falls back onto the planet. Spaceman Fred describes the path of the particle as a parabola using the laws of projectile motion. Spacewoman Kate recalls from Keplers laws that every bound orbit
around a point mass is an ellipse (or circle), and that the gravitation due to a uniform sphere is identical to that of a point mass. Which of the following best explains the discrepancy?

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24#
 
单选题 ( 1.0 分) (组内4/5) 切至整卷模式 搜藏此题  
  A turntable is supported on a Teflon ring of inn ;w ;t*gc).3b ljktt(i x dmowk.r6cq8er radius $R$ and outer radius $R+\sigma(\sigma << R)$, as shown in the diagram. To rotate the turntable at a constant rate, power must be supplied to overcome friction. The manufacturer of the turntable wishes to reduce the power required without changing the rotation rate, the weight of the turntable, or the coefficient of friction of the Teflon surface. Engineers propose two solutions: increasing the width of the bearing (increasing $\sigma$ ), or increasing the radius (increasing $R$ ). What are the effects of these proposed changes?



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25#
 
单选题 ( 1.0 分) (组内5/5) 切至整卷模式 搜藏此题  
  A hollow cylinder with a very thin wal.o5o 2fkrc xt4a0nmh( l (like a toilet paper tube) and a block are placed at rest at oc5a0( 2f.mnohx kr 4tthe top of a plane with inclination $\theta$ above the horizontal. The cylinder rolls down the plane without slipping and the block slides down the plane; it is found that both objects reach the bottom of the plane simultaneously. What is the coefficient of kinetic friction between the block and the plane?

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