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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 )3u(g y8ijmniid w-ng6pm(g5pc,zm- faucet, where the faucet is $10\,\mathrm{cm}$ 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 with initial velocity of magnite03v jg 0x v1ytjsiw;)ude $v_{0}$ 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. Friction is too himdy 19,su 5 nt3btgs,tgh for it to slide under any circumstance, but if the plane is sloped ent,9s3 u ms5b1tdy,gt nough 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 of equal mas3hxp)ip q gf(b* 1y9aos in the absence of external forces. Two particles emerge at a right angle to each othe)pxopyq3*9 ifag1h b(r 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 verqk)r*h )2*p t8mn(m6 d vo+n mokass-ytically, with the lower cannon pointing upward (towards the upper cannon) and the upper cannon pointing downward (towards the lower cannonrv+mm-n2p ynhq do ksts*8akom(6 * ))), $200\,\mathrm{m}$ 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 arrangedz4)/4 zwk8 3 wn :qfkjw96 uz:hmoqbkb vertically, with the lower cannon pointing upward (towards the upper cannon) and the upper cannon pointing downward (towards the lower cannon), z9u jwq: kkk4m/wq)w zfoz4n 3bb h86:$200\,\mathrm{m}$ 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 planethriss9snz8-.,ijn/ * fqmz9u has radius $R$ 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 0;7irf8+qt shumpq ik,q,go; inclined plane and allowed to roll without p f kmhsqqt;,iuq;7o08,+r gislipping to the bottom in the absence of rolling 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 pullmiq3h+w.)b ,e/3q+hboxqez iey to move a box with constant speei, /hx3oqh)m3e+q.e wbzi qb +d $v$. 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 the w y/g1ctui ,* :vhrjf)center. Two massless strings are attached to the hoop, one at A, the other at B. These strings are tied togeth h, wvrj i/gcy)1t*:ufer 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 the component of force versus53bu wt v ntxc7m9+m;s 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 radiuvxgq)36zsw5 8 6mejk ls $a$ 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 accelq i.mwa*e35vy 7w5 bdleration $\vec{a}$, 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 thez8f :l)kn0 gal 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 releasefgn):a zl8l k0d? Ignore air 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 sittin ;ay pcara 446(mr l.,mjttx*(pvr/f dg on a scale. 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 platform with a weig975czzes h;z xht 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 souf 2+li 7falw5mnd has an intensity 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 equipmenti vv6*/kd; pctson 9*nti *hj/ cannot be used to measure the local valk**oin*t 6tc9hp /iv/;v sjndue of the acceleration 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 thd4aofr zz .se3ip-v gy56:2(h 7z(vobh g;j bee sun shown below. Orbit P is circular with radbv y2 d .b;6eh zg-j3fo4hvsoz 5az7 i((:gperius $R$, 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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