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习题练习:2012美国US F=MA物理竞赛

 作者: admin 发布日期: 2025-11-02 12:14   总分: 25分  得分: _____________

答题人: 游客未登录  开始时间: 25年11月02日 11:40  切换到: 整卷模式

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1#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Consider a dripping faucet, where the faucet iscls8ffp ws / (uw*q.h2a-w(ts $10\,\mathrm{cm}$ above the sink. The time between drops is such that when one drop hits the sink, one is in the air and another is about to drop. At what height above the sink will the drop in the air be right as a drop hits the sink?

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2#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A cannonball is launched wik c.g4 dx(;197od*vpmo vf xxith initial velocity of magnitude $v_{0}$ over a horizontal surface. At what minimum angle $\theta_{min}$ above the horizontal should the cannonball be launched so that it rises to a height $H$ which is larger than the horizontal distance $R$ that it will travel when it returns to the ground?

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3#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An equilateral triangle is sitting on an inclined plane.5o f cawbjbzanngm;ma 9:+43( Friction is too high for it to slide undea4 b3jc(;nazwb a n:+m f5g9mor any circumstance, but if the plane is sloped enough it can "topple" down the hill. What angle incline is necessary for it to start toppling?

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4#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A particle at rest explodes into three particles v.(hd/ppe ,hz of equal mass in the absence of ezp,d/v hp. h(external forces. Two particles emerge at a right angle to each other with equal speed $v$. What is the speed of the third particle?

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5#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A $12\,\mathrm{kg}$ block moving east at $4\,\mathrm{m/s}$ collides head on with a $6\,\mathrm{kg}$ block that is moving west at $2\,\mathrm{m/s}$. The two blocks move together after the collision. What is the loss in kinetic energy in this collision?

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6#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two cannons are arranged vertically, with the lower cannon poinz7*ucdvd4-j pp *m e6ssuac17ting upward (towards the upper cannon) and the upper cannon pointing downward (topus*amd7u scz d6 7evjp1c*4-wards the lower cannon), $200\,\mathrm{m}$ above the lower cannon. Simultaneously, they both fire. The muzzle velocity of the lower cannon is $25\,\mathrm{m/s}$ and the muzzle velocity of the upper cannon is $55\,\mathrm{m/s}$.

How long after the cannons fire do the projectiles collide?

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7#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Two cannons are arranged vertically, with the lower cannon pointing78cqgg rw.-3 kr qsac9vn6a; p upward (towards the upper cannon) and the upper canq387 9s -q;gap6awrcc.rv kgnnon pointing downward (towards the lower cannon), $200\,\mathrm{m}$ above the lower cannon. Simultaneously, they both fire. The muzzle velocity of the lower cannon is $25\,\mathrm{m/s}$ and the muzzle velocity of the upper cannon is $55\,\mathrm{m/s}$.

How far beneath the top cannon do the projectiles collide?

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8#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A block of mass $m=3.0\,\mathrm{kg}$ is moving on a horizontal surface towards a massless spring with spring constant $k=80.0\,\mathrm{N/m}$. The coefficient of kinetic friction between the block and the surface is $\mu_{k}=0.50$. The block has a speed of $2.0\,\mathrm{m/s}$ when it first comes in contact with the spring. How far will the spring be compressed?

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9#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A uniform spherical planet has radiiec)d 9e-c;aw bo o jp3l9w(y7us $R$ and the acceleration due to gravity at its surface is $g$. What is the escape velocity of a particle from the planet's surface?

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10#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Four objects are placed at rest at the top of an inclined plane anxmv gzl6a0k 9d.pvo 6.d allowed to roll without slipping to the bottom in the absence of rozldvv x6g kpom9 .a.06lling resistance and air resistance.
* Object A is a solid brass ball of diameter $d$.
* Object B is a solid brass ball of diameter $2d$.
* Object C is a hollow brass sphere of diameter $d$.
* Object D is a solid aluminum ball of diameter $d$. (Aluminum is less dense than brass.)
The balls are placed so that their centers of mass all travel the same distance. In each case, the time of motion $T$ is measured. Which of the following statements is correct?

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11#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  As shown below, Lily is using the rope through a fixed pulley to move)n uk/ffoc- n9;n7qsvh +q xl5et.1rx a box with constant speed x7or;hl +9)5vqun1ec-. xtf knf sn/q$v$. The kinetic friction coefficient between the box and the ground is $\mu < 1$; assume that the fixed pulley is massless and there is no friction between the rope and the fixed pulley.

Then, while the box is moving, which of the following statements is correct?

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12#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A rigid hoop can rotate about ku dil0-yvk(rtjbq;adm:deb (u;,z s j8 2l0 .the center. Two massless strings are attached to the hoop, one at A, the akr;(bk 0zte2s8 0ydjdd iq,:;-.luu(bjvml other at B. These strings are tied together at the center of the hoop at O, and a weight G is suspended from that point. The strings have a fixed length, regardless of the tension, and the weight G is only supported by the strings. Originally OA is horizontal.

Now, the outer hoop will start to slowly rotate $90^{\circ}$ clockwise until OA will become vertical, while keeping the angle between the strings constant and keeping the object static. Which of the following statements about the tensions $T_{1}$ and $T_{2}$ in the two strings is correct?

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13#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Shown below is a graph of iw/ 2c) dgp.l 5jfy3d2ycbp+q the component of force versus position for a $4.0\,\mathrm{kg}$ cart constrained to move in one dimension on the $x$ axis. At $x=0$ the cart has a velocity of $-3.0\,\mathrm{m/s}$ (in the negative direction).

Which of the following is closest to the maximum speed of the cart?

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14#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A uniform cylinder of radius p/j)jtucd-x. (:ymyr3ok 3d v$a$ originally has a weight of $80\,\mathrm{N}$. After an off-axis cylinder hole at $2a/5$ was drilled through it, it weighs $65\,\mathrm{N}$. The axes of the two cylinders are parallel and their centers are at the same height.

A force $T$ is applied to the top of the cylinder horizontally. In order to keep the cylinder is at rest, the magnitude of the force is closest to:

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15#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A car of mass $m$ has an engine that provides a constant power output $P$. Assuming no friction, what is the maximum constant speed $v_{max}$ that this car can drive up a long incline that makes an angle $\theta$ with the horizontal?

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16#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Inside a cart that is accelerating horizontally at accelerationo/9r *.mgxagqh6 wco8 $\vec{a}$, there is a block of mass $M$ connected to two light springs of force constants $k_{1}$ and $k_{2}$. The block can move without friction horizontally. Find the vibration frequency of the block.


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17#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Shown below is a $log/log$ plot for the data collected of amplitude and period of oscillation for certain non-linear oscillator.

According to the data, the relationship between period $T$ and amplitude $A$ is best given by

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18#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A mass hangs from the tx(i ba(jfw;97b-n1jr(y x do ceiling of a box by an ideal spring. With the box held fixed, the mass is given an initial velocity and oscillates with purely vertical motion. When the mass reaches the lowest point of its motion, the box is released and allowed to fall. To an observer inside the box, which of the following quantities does not change when the box is released? Ignore d1ay (bj frjx9bx7( -(; wnoitair resistance.

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19#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A $1,500\,\mathrm{Watt}$ motor is used to pump water a vertical height of $2.0\,\mathrm{meters}$ out of a flooded basement through a cylindrical pipe. The water is ejected though the end of the pipe at a speed of $2.5\,\mathrm{m/s}$. Ignoring friction and assuming that all of the energy of the motor goes to the water, which of the following is the closest to the radius of the pipe? The density of water is $\rho = 1000\,\mathrm{kg/m^{3}}$.

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20#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A container of water is sitting on a sfy)ygf hpq0k( y xe9+j(1w9yucale. Originally, the scale reads $M_{1}=45\,\mathrm{kg}$. A block of wood is suspended from a second scale; originally the scale read $M_{2}=12\,\mathrm{kg}$. The density of wood is $0.60\,\mathrm{g/cm^{3}}$; the density of the water is $1.00\,\mathrm{g/cm^{3}}$. The block of wood is lowered into the water until half of the block is beneath the surface.

What is the resulting reading on the scales?

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21#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A spring system is set up as follows: a pla6e9*g 1*tia 4lgllihr : m)wwb b3xug6tform with a weight of $10 N$ is on top of two springs, each with spring constant $75 N/m$. On top of the platform is a third spring with spring constant $75 N/m$. If a ball with a weight of $5.0 N$ is then fastened to the top of the third spring and then slowly lowered, by how much does the height of the spring system change?


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22#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The softest audible sound has an intenu: rb5)d bng.3e bh6ba3q8wjbsity of $I_{0}=10^{-12} W/m^{2}$. In terms of the fundamental units of kilograms, meters, and seconds, this is equivalent to

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23#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Which of the following sets of equipment cannot be used to measure the cvfz 4dta( njh+(*x2/ 3wpkf wlocal value of the acceleratio(/cw3 x*h zk+ a(jpdfnt2vw4f n due to gravity ($g$)?

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24#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Three point masses $m$ are attached together by identical springs. When placed at rest on a horizontal surface the masses form a triangle with side length $l$. When the assembly is rotated about its center at angular velocity $\omega$, the masses form a triangle with side length $2l$. What is the spring constant $k$ of the springs?

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25#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Consider the two orbits around the sun shown below. Ot(5q1g :bdjzfrbit P is circular with radd5(q:zfgb j1 tius $R$, orbit Q is elliptical such that the farthest point $b$ is between $2R$ and $3R$, and the nearest point $a$ is between $R/3$ and $R/2$. Consider the magnitudes of the velocity of the circular orbit $v_{c}$, the velocity of the comet in the elliptical orbit at the farthest point $v_{b}$, and the velocity of the comet in the elliptical orbit at the nearest point $v_{a}$. Which of the following rankings is correct?


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