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    20 April 2023 Volume 42 Issue 2
      
    Motion characteristics of Lagrange gyroscope based on analytical results
    XIONG Yong-jian
    College Physics. 2023, 42(2):  1.  doi:10.16854/j.cnki.1000-0712. 220367
    Abstract ( 343 )   PDF (314KB) ( 331 )  
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    In this paper,the analytical method of Lagrange gyroscope motion equation is established.The condition for regular precession of Lagrange gyroscope is derived,and the analytical solution for nutation with small angle and precession near regular precession is obtained by series expansion technique.A concise picture of the gyroscope rotation axis motion is given,that is,the superposition of the regular precession around the vertical axis caused by gravity and the free precession without gravity. According to the analytical solution,the mystery of the gyroscope not falling down is explained.

    Discussion on the teaching of thermodynamic properties of the rubber band
    TU Fei-quan, YANG You-chang, WAN Meng, SUN Bin, HUANG Qi-hong
    College Physics. 2023, 42(2):  6.  doi:10.16854/j.cnki.1000-0712.220088
    Abstract ( 454 )   PDF (231KB) ( 314 )  
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     Based on the first and second laws of thermodynamics and Maxwell relation, the thermodynamic properties of the rubber bands are systematically discussed. We also briefly introduce the micro-model of the rubber band elasticity. These methods and conclusions will help students to better understand and master the basic knowledge and methods of thermodynamics, and also avail students to test the correctness of these conclusions by the experiments designed by themselves
    Numerical analysis of momentum probability distribution of  particle in infinite deep potential well
    LU Fa-lin, CHEN Chang-yuan
    College Physics. 2023, 42(2):  10.  doi:10.16854/j.cnki.1000-0712.220343
    Abstract ( 553 )   PDF (281KB) ( 492 )  
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    The momentum of the eigenstate particle in the one-dimensional infinite deep potential well presents a symmetric and continuous distribution of negative infinity to positive infinity symmetry with countless nodes. The dimensionless momentum probability density distribution of the eigenstate particle is generally composed of two main peaks and numerous small peaks. Both the classical momentum and the most probable momentum are distributed in the region of the main peak. Numerical results show that the probability limit of momentum spectrum in two main peak regions is about 0.9028. The more the number of small peaks included in the measurement is, the closer the probability of the particle appearing is to 1. The classical momentum distribution of particle is the limit of the quantum momentum distribution under the condition of  high measurement accuracy and large quantum number.

    A simple example to understand relational space-time
    CHEN Hong-bin
    College Physics. 2023, 42(2):  15.  doi:10.16854/j.cnki.1000-0712.220282
    Abstract ( 485 )   PDF (174KB) ( 221 )  
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    Galilean velocity transformation is correct when space and time are absolute. This paper analyzes a common example from the perspective of worldview, in which Galilean velocity transformation is incorrect.The conflict between worldviews is pointed out, which leads to the reconstruction of a self-consistent worldview containing a relational view of space-time.

    Solving resonance circuit through calculation of trigononmetric functions
    LIU Zhi-guo, ZHAO Jing-geng, ZHANG Yao-hui, WANG Xian-jie, ZHANG Ling-li, HUANG Xi-qiang, WANG Xiao-ou, ZHANG Yu
    College Physics. 2023, 42(2):  18. 
    Abstract ( 281 )   PDF (371KB) ( 177 )  
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    In electromagnetism teaching, the resonance circuit is usually solved by using vector diagram or complex number method, which demands the knowledge of rotating vector or complex representation for oscillations, respectively. A direct method is introduced in this paper, i.e., the solution is obtained by straightforward calculation of oscillation functions (trigonometric functions). The method can be extended to general alternative current circuit. The method demands less preliminary knowledge, and may be suitable for the course of “College Physics” for majors other than physics. 

    Understanding free energy minimum principle from symmetry of crystals
    FAN Bao-lu, ZHANG Qian-wen, SHAO Shan-shan, LIU Yang
    College Physics. 2023, 42(2):  24.  doi:10.16854/j.cnki.1000-0712.220283
    Abstract ( 399 )   PDF (292KB) ( 199 )  
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    Free energy and crystals are important contents in the teaching of basic physics. Crystals are thermodynamically stable solid state systems, which are three-dimensional periodic stacking of large numbers of atoms. The diversity of interactions between atoms indicates that the threedimensional periodic stacking of atoms should be determined by universal factor, which is the law of nature. It is emphasized that the three-dimensional periodic stacking of atoms is the geometric equivalent of the principle of minimum free energy of the system. It is aimed to cultivate students to discover the inner connection of things, and to explore the laws of physics behind natural phenomena.

    Theory background and Matlab coding of temporature  extrapolation method for fusion heat of ice 
    FENG Fei-long, HUANG Yu-hong, JIN Wei, WANG Gong-zheng, CUI Zhi-yuan
    College Physics. 2023, 42(2):  28.  doi:10.16854/j.cnki.1000-0712.220377
    Abstract ( 501 )   PDF (253KB) ( 272 )  
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     The theory background of temperature extrapolation method usually used for heat of fusion measurement of ice is elaborated based on Newtons law of cooling. The corresponding Matlab codes are provided and applied in data processing of experiment results measured by digital thermometer. Regarding to the obtained temperature-time graph, the area-equavalence requirement of the method can be ensured and the results are obtained in expected accuracy. It is found that the approach is insensible to ice and water masses as well as the ice-casting temporature, while the ambient temperature although affects the measurement of thermal convection coefficients, has little effects on temperature extrapolation as well as the corresponding results.
     
    On the development of centripetal force
    LIU Ning
    College Physics. 2023, 42(2):  32.  doi:10.16854/j.cnki.1000-0712.220227
    Abstract ( 439 )   PDF (208KB) ( 438 )  
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    Centripetal force is an important concept in mechanics. By considering the understanding of centripetal force in three different historical periods, this paper clearly shows that the centripetal force has undergone a tortuous but deepening process along with people,s understanding of basic motion and mechanical laws. It is shown that the concept of centripetal force as a bridge emphasizes its important role in the development of kinematics to dynamics. In particular, the development of the concept of centrifugal force to centripetal force is a revolutionary breakthrough, which promotes the establishment of the three laws of mechanics under the inertial system, and is a key step for Newton to discover the law of universal gravitation. 
    Design of visualized numerical experiments for wave packet scattering in quantum mechanics
    DENG Zhi-jiao, ZENG Jun-xiang, JIANG Yue-qian, CHEN Ping-xing, LIU Wei-tao
    College Physics. 2023, 42(2):  36.  doi:10.16854/j.cnki.1000-0712.210615
    Abstract ( 435 )   PDF (339KB) ( 241 )  
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     In view of the lack of discussion of wave packet scattering in commonly used quantum mechanics textbooks, this article takes a one-dimensional delta potential well as an example to introduce how we design numerical experiments for wave packet scattering in the seminar teaching, in order to help students establish the physical image of quantum scattering by themselves.

    Study on the cause of the quasi-2400-year cycle of the Sun orbital motion without bypassing the mass center of the solar system
    LIU Fu-gang, YAO Yun-long, BAO Kun-shan, WANG Wei-min,
    College Physics. 2023, 42(2):  40.  doi:10.16854/j.cnki.1000-0712.220262
    Abstract ( 301 )   PDF (527KB) ( 226 )  
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    According to the study on the eigenvalues of the K index, it is found that the larger K index indicated the greater synodic degree of the planetary system in a certain radial direction. The variation of the solar orbit radius calibrated by the extreme value of the K index has a significant nesting relationship of quasi20a, 179a and 2400a periods. With the increase of time scale, the maximum of K index shows a significant quasi2400a period, and the duration of the mass center of the solar system inside and outside the solar body also has a quasi2400a period. This implies the quasi2400a period of the solar orbital motion without bypassing the mass center of the solar system. Previous reports about variation in the distance between the Sun and the mass center of the solar system (including K-index images) have failed in revealing this rule. In this paper, taking the connection between Jupiter and the Sun as the reference direction, the planetary synodic vector index K is established. The K-vector index image clearly shows the quasi2400-year cycle of the Sun orbital motion without bypassing the mass center of the solar system, which is composed of 13~14 quasi179a envelope periods (the trough K values of 3~4 periods appear < 0). This discovery is a further step forward in the scientific identification of the complex characteristics of the Suns orbital motion.


    Public optional course “Exotic Quantum World”:teaching practices and exploration
    LI Jie-sen, ZHU Chuan-yun, LIN Jie-li, LIU Yu-hua
    College Physics. 2023, 42(2):  46.  doi:10.16854/j.cnki.1000-0712.220087
    Abstract ( 311 )   PDF (412KB) ( 465 )  
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     As quantum technology enters the public’s horizon, an increasing attention is paid to quantum theory among the general public. Besides, some college students also show their interest on quantum physics. Under the circumstances, Foshan University managed to make the quantum-related courses available to students of non-physics majors so as to broaden their horizons and cultivate their rigorous scientific attitude and the consciousness of innovation. In this paper, the teaching practice of Exotic Quantum World in university is taken as an example, and the attempts and explorations to the reform and renovation are demonstrated so as to guide the students into quantum world. According to the survey after the course, 90% of students are interested in the course. Thus, it can be seen that these efforts achieve certain results.

    Online and offline collaborative teaching mode and  multi-modal data evaluation system
    XIN Jun-li, LI Yong-hong, WANG Xiao-ping
    College Physics. 2023, 42(2):  52.  doi:10.16854/j.cnki.1000-0712.220134
    Abstract ( 286 )   PDF (710KB) ( 213 )  
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     Under the background of intellectual education, the teaching mode and teaching evaluation method of mechanics are studied in this paper. On-line and off-line collaborative teaching mode and multi-modal data evaluation system based on Rain Classroom are proposed. Taking the teaching practice of mechanic course in Yuncheng University as an example, the teaching management and teaching effect are introduced in detail. It is found that online and offline collaborative teaching mode realized the progressive teaching idea from pre-class, in-class to after-class and course evaluation, organically integrating knowledge, ability and quality. Moreover, teachers can effectively track students learning behavior in whole term by multi-modal data evaluation system, which simultaneously provides data support for the teaching of multi-dimensional different levels and various process evaluation. 

    Quantitative simulation analysis of magnetic flux leakage detection  for wire rope based on finite element method
    JIA Rong-rong, YANG Shu-pei, GUO Ze-hong, LI Guo-xuan, HUANG Kai-jie, PENG Li,
    College Physics. 2023, 42(2):  59.  doi:10.16854/j.cnki.1000-0712.220117
    Abstract ( 319 )   PDF (984KB) ( 165 )  
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     Magnetic flux leakage (MFL) testing is a common method in nondestructive testing of wire rope. Based on the basic principle of MFL detection and threedimensional magnetic dipole model, this paper realizes  the visualized online detection of wire rope by using By~Bz diagram. The characteristics of MFL defects of different lengths, widths and depths are obtained by using finite element simulation method, the quantitative relationship between the MFL circle in By~Bz diagram and the degree of defects is established. The difference of magnetic leakage caused by internal and external defects of wire rope is discussed, and experimental verification is carried out in order to provide a new theoretical basis for quantitative identification of wire rope damage and judgment of internal and external defects.