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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: 游客未登录  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 constant r.t :p+x-dif.1do 5rn:ebhi a 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 te *.tw uwa; 400zerotr6jl x k+6olcf7rn 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 second i8-/ kpjkc5( do yi6h)dp5qdgkv; 6- i iebr1linterva-/-i k6p qv5ebdic 5iry hd8g;1k)o(i jkdlp 6l.

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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 distanc.o*/ uyqip7fyo edx i, 1yfr+)e traveled 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 in a circular orbit about tdl,lybeam,8 wln r1 *3he Sun at constal*1,yrm 3n 8bweladl,nt speed, 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 wit xo3fgag 68ls8h velocity $v_{\mathrm{c}}$ 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 wit d,:fmdk)+r zhh an angular velocity $\omega_{0}$ 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 winbmng4 f iauo6 x,kzg;2;m1f*th 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 equilibrium length of 2.0 meterh 7s)zhe1 p*nos and a spring constant of 10 newtons/meter. Alice is pul sphn)*h7zo1eling on one end of the spring with a force of 3.0 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 result in an increase in the per7fn z.jhqo3x2oe p+ *gnfo+7oiod of a simple pendulqfgf zo7e2n+ xo+.n hopj7*o3 um?

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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 cylindrical cup floats in a rectangular tub half-fille*ht-vt7e mk 5. :-inyvxnb)s9soeu .jd 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-.:i5xn*evsbv.t7jm h)oyutkn-s e9 represent the water level in 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 collection of identical he m6b2r*sf5vpdfo ,z o k1q8so.gcz4q-avy balls and lightweight rods. When two balls are placed at the ends of one rod and interactz6 8 mpbcfkq oos1sd*,o4 v2-.5gzrfq 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 an 5f tqv gxj4)whk4j+- solid cylinder 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 st3xxemldj4lxvjy 56 /.rd;)8 m3q ggky rings with weights tied at various point, all hanging from the ceiling, and reakmr6g m) x8ey/l3qdjl ;5 4gx.xvd3jyching 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 the 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 displah,b f)fukq* 2f8rpssnvw s0,7 ced $2.0 \mathrm{~cm}$ 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 thl;3cs w-xu*;amv yjf 6e physics book to keep the rope from uxsfja-cl yv3w;6;m* slipping?

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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 force that is just enough to keep the rope fqd*wnrysn+fd+*z3 f0 rom 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 stds*+n nf3z 0dr *+fyqwart slipping from Jonathans hand. At what speed does the 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 retur k6 vh)jqtvzj 3pkhfvtdi14+ox,5/+sn to the 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 distance bet/ nba+j;(w -bnqihck)w,6 oylb8y6dc.pz a)cween 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 qx :fk2oqd9+pjc68 myfixed 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 torque o9ncro a(zv)rbud4 .i u*oqsl l;j 2)+gutput of a hypothetical gasoline engine as a function of rotation frequency. The engine is incapable lan;odz94(2r.vubo*ciguqj +))rls of running outside of the graphed range.


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 surf6dsc oxa9c fu,+re1lb) ;s 2wxace of a uniform, stationary spherical planet at an angle to the vertical. The particle travels1 uoew)f+cxsc26rld x,9;s b a 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 invq8w:mx0cix4x uknxk4x c*bqw 3+(s 0ner 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 v p;,a v p3av4vko3xn-roh/i 0dery thin wall (like a toilet paper tube) and a block are placed at rest at the top of a plane with i dar-v x4ih ;o0,ap n3kop3vv/nclination $\theta$ 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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