Physicsbow物理碗竞赛真题解析 想拿就要看看这些考生常错的错题

马上就要到20212年了，在新的一年也有很多竞赛都重新开启了，同学们有没有好好复习呢？下面给大家带来一些Physicsbow物理碗竞赛真题，这些真题是根据历年考生经常错的整理而成，如果有复习的同学记得赶紧来看看自己是否会犯同样的错。

Physicsbow物理碗竞赛真题

A monatomic ideal gas is the working substance for a refrigerator that undergoes the cyclic process (ABCDA) shown in the PV diagram. The processes are all isochoric or isobaric with pressures between 图片and 图片 and volumes between 图片and 图片. What is the coefficient of  performance for this refrigerator?

摘自2021年44题

(A)1/4  (B)1/3  (C)4/3  (D)11/2  (E)13/2

本题考查知识点：COP的概念，理想气体状态方程，单原子理想气体的等压、等容摩尔热容。

要点解析：

对于单原子理想气体：

由理想气体状态方程可得：

因此，COP=11/2.

Two clocks, A and B, are synchronized on Earth. Clock A is placed onto a space ship that leaves Earth in a straight line with a speed of  . On Earth, a scientist with clock B has her telescope fixed directly on clock A. If each clock started at , what time does the scientist observe on clock A when clock B reads  ? Assume the time of acceleration for the ship leaving the Earth was negligible.

摘自2014年50题

(A) 24 s    (B) 30 s   (C) 50 s   (D) 54 s   (E) 72 s

本题考查知识点：物理过程的分析，钟慢效应和固有时, 尺寸收缩效应

要点解析：分析物理过程可知，clock B的读数应该包含两部分，即飞船走距离的时间和光返回的时间，，解得此时。于是，.由于飞船测量其行走距离历时为固有时，根据钟慢效应则有. 或者根据尺寸收缩效应，飞船测得的距离

思维定式

A small object of mass 11.0 g is at rest 30.0 cm from a horizontal disk's center. The disk starts to rotate from rest about its center with a constant angular acceleration of 4.50 rad/s2. What is the magnitude of the net force acting on the object after a time of t=1/3 s if the object remains at rest with respect to the disk?

摘自2013年23题

解析：该转动具有角加速度，不是匀速，因此合力应该由径向（向心）和切向两部分组成。

A frictionless, solid disk pulley has a mass of 7.07 kg, a radius of 66.0 cm, and is free to rotate vertically about an axle. A rope is wrapped around the disk, a 1.53 kg mass is attached to the end of the rope, and the mass is allowed to fall vertically. What is the angular acceleration of the pulley?

(A) 4.58 rad/s2   (B) 7.98 rad/s2  (C) 9.87 rad/s2  (D) 2.25 rad/s2  (E) zero

摘自2018年20题

解析：对于绳子连接的两个物体，它们的运动具有一致性，应该分别做受力分析，而不应该想当然的认为绳子的拉力即为悬挂物体的重力。

概念掌握不牢

A constant force F=50N(as shown in the figure) is applied for the 6.0 meter motion of the box upward along the incline. The mass of the block is M=15KG. Which one of the following choices best represents the work done by the force F on the box for the motion?

摘自2012年16题

(A)300J  (B)282J  (C)260J  (D)193J  (E)150J

解析：功的定义 图片 中 图片 角度没有掌握，不知道对应于该题中的哪个角度。

A crate gains 36.0J of kinetic energy while its speed is increased from 2.00 to 4.00. Which one of the following choices best represents the mass of the crate?

摘自2014年11题

(A) 36.0 kg  (B) 18.0 kg  (C) 6.0 kg  (D) 3.0 kg  (E) 1.5 kg

解析：记错动能的公式，

正确公式应为

知识点欠缺

Which one of the following statements best describes Huygens’s Principle?

摘自2013年24题

(A) An additional pressure is transmitted undiminished to all points in the fluid and to the walls of the container.

(B) Each point on a wavefront acts as a source of secondary spherical wavelets (new waves).

(C) For every action force, there is an equal but opposite reaction force.

(D) It is impossible to have a process which has the sole result of transferring energy from a low temperature reservoir to a high temperature reservoir.

(E) A time-changing magnetic field has an associated induced electric field.

The principal quantum number of an electron is n=5.How many possible values of the orbital magnetic quantum number are there for this electron?

摘自2013年36题

(A) 25  (B) 11  (C) 9  (D) 5  (E) 4

审题不严谨

For the figure shown, the variable resistance of the inner circuit,  is increasing at a constant rate. While this is occurring, in which direction is the magnetic field associated with the inner circuit at the point P in the plane of the circuit and in which direction is the flow of electrons through the resistor labeled .

摘自2013年35题

解析：电子流动的方向而非电流的方向

An object moves with constant acceleration starting with velocity  and ending with a velocity of in a time of 3.00s. For this motion, what is the average speed associated with the object?

摘自2014年33题

(A) 2.00 m/s  (B) 2.17 m/s  (C) 2.50 m/s  (D) 2.83 m/s  (E) 3.00 m/s

解析：平均speed而非平均velocity

以上就是历年的考生在考试中常常会做错的错题，同学们如果你也在复习物理碗竞赛，除了一些必要的知识点以外，对于以上这些错题也要特别注意，不要丢分哦。离物理碗考试还有几个月的时间，同学们现在好好准备还来得及考试。想了解更多有关物理碗竞赛复习信息吗？赶紧点击【预约试听】报名唯寻的竞赛复习班吧！

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