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- The disenchanted aacceleration in analytical mechanics
- ZHANG Xiao-bing
- College Physics. 2020, 39(05): 1-3. doi:10.16854 /j.cnki.1000-0712.190442
- Abstract ( 1357 ) PDF (167KB) ( 727 )
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- Splittings of atomic energy levels caused by the magnetic hyperfine interaction and diagram drawing of the splitted energy levels
- SUN Zhen-dong, TIAN Yu-feng
- College Physics. 2020, 39(05): 4-9. doi:10.16854 /j.cnki.1000-0712.190371
- Abstract ( 2664 ) PDF (627KB) ( 1630 )
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- Several“Pythagorean theorems”in special relativity
- ZHOU Guo-quan
- College Physics. 2020, 39(05): 10-13. doi:10.16854 /j.cnki.1000-0712.190395
- Abstract ( 2508 ) PDF (214KB) ( 930 )
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- The Fourier-Bessel integral expansion of a function in semi-infinite space
- JIANG Xiang-qian, HOU Chun-feng, MENG Qing-xin, ZHANG Yu
- College Physics. 2020, 39(05): 14-15. doi:10.16854 /j.cnki.1000-0712.190248
- Abstract ( 2585 ) PDF (147KB) ( 1151 )
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- Twin paradox and interstellar travel
- QIN Li, LIN Ran-xi, GAN Xiao-long, ZHU Hu
- College Physics. 2020, 39(05): 16-19. doi:10.16854 /j.cnki.1000-0712.190225
- Abstract ( 1257 ) PDF (286KB) ( 624 )
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- Study of the critical density and stability of suspension in standing wave sound field
- JIN Shuo, YAN Qi-qi, LI Cheng-yi, ZHANG Zhao-hang, HUANG An-ping
- College Physics. 2020, 39(05): 20-26. doi:10.16854 /j.cnki.1000-0712.190546
- Abstract ( 1243 ) PDF (1378KB) ( 1124 )
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- Teaching research on simulation experiment of electrostatic field
- LI Li, ZHANG Hao-jing, ZHANG Xiong, QIU Long-bin, WU Yang-feng
- College Physics. 2020, 39(05): 27-30. doi:10.16854 /j.cnki.1000-0712.190545
- Abstract ( 1989 ) PDF (195KB) ( 691 )
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- Measuring the magnetic field of Helmholtz coil with the magnetic sensor of a smart phone
- LIU Wei, CHENG Min-xi
- College Physics. 2020, 39(05): 31-32. doi:10.16854 /j.cnki.1000-0712.190402
- Abstract ( 1572 ) PDF (986KB) ( 946 )
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- An easy-to-understand teaching method about entropy
- DONG Zhan-hai
- College Physics. 2020, 39(05): 33-37. doi:10.16854 /j.cnki.1000-0712.190409
- Abstract ( 1377 ) PDF (435KB) ( 767 )
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- Teaching reform and exploration of Poisson equation based on flipped classroom mode
- CHANG Jun-li, DONG Ning, ZHOU Chun-qiong, ZHANG Hua
- College Physics. 2020, 39(05): 38-43. doi:10.16854 /j.cnki.1000-0712.190354
- Abstract ( 1092 ) PDF (592KB) ( 581 )
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- Quantitative detection of trace crude oil in the sand using reflected terahertz time-domain spectroscopy
- LI Xin-yu, ZHAN Hong-lei, ZHANG Yan, REN Ze-wei, ZHAO Kun, JIAO Yu-qiu
- College Physics. 2020, 39(05): 44-46. doi:10.16854 /j.cnki.1000-0712. 190303
- Abstract ( 866 ) PDF (1066KB) ( 366 )
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- The colors in“A panorama of Rivers and Mountains” ———Teaching physics with an interdisciplinary approach
- WEI Ran
- College Physics. 2020, 39(05): 47-51. doi:10.16854 /j.cnki.1000-0712.190493
- Abstract ( 2414 ) PDF (737KB) ( 744 )
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- Spring-mass oscillator confined to horizontal frictionless plain
- XU Shi-hao, ZHANG Xiong
- College Physics. 2020, 39(05): 52-57. doi:10.16854 /j.cnki.1000-0712.190309
- Abstract ( 1914 ) PDF (980KB) ( 1566 )
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- Influence of inhomogeneity of the dip angle and the friction coefficient on the core result of Galileo's inclined plane experiment
- ZHANG Run, ZHANGYANG Yu-ying, XIONG gang
- College Physics. 2020, 39(05): 58-61. doi:10.16854 /j.cnki.1000-0712.190368
- Abstract ( 1398 ) PDF (624KB) ( 623 )
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- Effect of massive string and pulley on the motion of Atwood machine
- WANG Jie, HE Xi-ping
- College Physics. 2020, 39(05): 62-65. doi:10.16854 /j.cnki.1000-0712.190258
- Abstract ( 975 ) PDF (348KB) ( 709 )
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- An improvement to the verification of parallel axis theorem for moment of inertia
- YAN Min, DAI Yu-qin, YUAN Jun, WANG Xiao-xiong
- College Physics. 2020, 39(05): 66-69. doi:10.16854 /j.cnki.1000-0712.190392
- Abstract ( 3469 ) PDF (733KB) ( 2222 )
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- Design and Production of the liquid-resistivity measuring device
- WANG Shu-guang, SUN Li-yuan, BAI Jing-zhao, REN Bo, SONG Yang
- College Physics. 2020, 39(05): 70-73. doi:10.16854 /j.cnki.1000-0712.190245
- Abstract ( 1290 ) PDF (667KB) ( 1126 )
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- Autocollimating Method Based on Lateral Moiré Fringe
- ZHU Chao-yi, LU Wei-xin, GAO Hong, WANG Mei
- College Physics. 2020, 39(05): 74-77. doi:10.16854 /j.cnki.1000-0712.190264
- Abstract ( 1147 ) PDF (731KB) ( 661 )
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By using the Lagrangian approach to classical mechanics，we investigate the
condition of static equilibrium

and the continuum dynamics，respectively. By using Hamiltonian approach，we introduce the distinct

point of equilibrium as well as the stable ensemble distribution，which makes sense in the scope of statistical mechanics，

in the phase space.The examples show that the concept of acceleration is disenchanted in the framework of

analytical mechanics.Also，the so-called“equilibrium states”are found to be realized by the different ways from

the case of Newtonian approach.

Hyperfine interaction is one of the important contents in the course of“Atomic
Physics”. So far in

domestic and foreign textbooks of atomic physics，authors just write down the expressions of splittings of atomic energy

levels caused by the magnetic hyperfine interaction without and with an external magnetic field，and show some

related research examples. Here，for the cases of without and with a weak or a strong external magnetic field，the

derivation processes of these formulas and discussions about diagram drawing of these splitted energy levels are described

in details. The contents in this paper will be helpful for teachers and students in understanding and truly

mastering the related parts of knowledge in the course of“Atomic Physics”.

Some teaching experiences about electrodynamics and special relativity are
summarized. Several relativistic

invariants and“Pythagorean theorems”in special relativity are derived by means of the tensor theory in

four - dimensional Minkowski space and the contraction operation rules of these tensors. Meanwhile， some

application examples are given in illustration of these formulae.

In cylindrical coordinates，the family of intrinsic Bessel function constitutes
a complete orthogonal
function series，which can be used as the bases of generalized Fourier
expansion. In this paper，starting from the generalized Fourier expansion of a
function defined on a finite interval and using the approximate formula of
Bessel
function and its zero point formula，we discuss the Fourier-Bessel integral
expansion of a function defined in semiinfinite
space，and get the approximate expression of module square of Bessel
function. In the asymptotical situation，
discontinuous parameter becomes continuous one，we obtain the Fourier-Bessel
integral and coefficient
formula of the function.

The time discrepancy associated with the“Twin Paradox”in two hypothetical
interstellar travel programs，
is calculated. This result reflects an absolute difference about the time
experienced between inertial and noninertial
reference frames，rather than a " relative" effect correlating the two
references.

In this paper，the object in the sound field is studied，and the acoustic
radiation pressure equation

is theoretically derived both in the travelling wave and the standing wave. The concept of the critical suspension

density is introduced into the standing wave sound field，which should be used as a criterion for suspension in a

nonlinear sound field. At the same time，the maximum range of Resonant cavity's movement speed is given. Furthermore，

by the combination of numerical computations and experimental results，the influence of the density and the

size of the sample in the standing wave sound field，the shape of the emitting surface and the reflecting surface，the

distance between these two surface，and the size of the reflecting surface on the suspension stability are investigated.

It is found that when the size and the density of the object are determined，adjusting the length of the resonant cavity

and increasing the sound pressure at the antinode are effective means to improve the acoustic suspension stability.

Simulation of electrostatic field with a steady current field is a very classic
general physics experiment.

In the traditional physics experiment，the experimental data was generally recorded by an equal arm recording method，

and then the inner cylinder radius and the outer ring inner radius were obtained according to the linear relationship

between the equipotential voltage and the logarithm of the equipotential circle radius. According to the characteristics

of the experimental data，the exponential fitting method，the binary linear regression method and the A-type

uncertainty method are simultaneously sued to process of the experimental data obtained by simulating the electrostatic

field with the steady current field. The static current field is simulated and error analysis of field experiments is given.

Through comparison，the application and analysis of data processing methods in experiments are carried out.

The magnetic sensor in the smart phone is located by a pre-experiment. The
magnetic field distribution
throughout the axle wire of Helmholtz Coil is measured，Biot-Savart Law and
magnetic field’s superposition
principle are verified by a handy and precise new measurement method.

The entropy，like force，energy and momentum，is an important concept in physics.
If a simple and

understandable method could be designed，it is useful for teaching physics for liberal arts. In this paper，an easy-to

-understand teaching method about the entropy is proposed. Therefore，the concept of entropy can be taught without

the needing for students to learn the second law of thermodynamics. The corresponding teaching design is as follows: introducing the concept of entropy ( namely，Boltzmann entropy) through daily life examples，designing two examples for students to calculate the entropy，making students fully understand the meaning of entropy through discussion on specific problems，obtaining the Clausius entropy from Boltzmann entropy through an example，designing an entropy demonstration experiment to strengthen teaching effect，and connecting the entropy with environmental protection to make physics humanistic，and finally specifying the different levels of entropy calculation. Problem-based learning ( PBL) is adopted in the teaching design.

During many years of teaching practice，it was found that some undergraduates
were often faced

with difficulties in learning Poisson equation，such as difficult knowledge points，fast teaching progress and no way

to start self-study. In view of the situation，flipped classroom mode is introduced in the teaching of Poisson equation

for teaching reform and the scheme of teaching design is primarily explored for achieving superior teaching effect.

The contamination of crude oil in the sea is a major threat to marine organism
and the environment

safely. The detection of crude oil in the sand near the sea is of significance to petroleum exploration and environmental

protection. Reflected terahertz time-domain spectroscopy is used for the quantitative detection of the crude

oil in the sand. A detailed analysis is performed about the delay time and wave velocity across the sample. The research

indicates that the relationship between the crude oil concentration and the delay time shows linear decrement

character，the reflected terahertz time-domain spectroscopy is a potential method for quantitative detection in the

environmental protection.

The famous painting“A Panorama of Rivers and Mountains”of the Northern Song
Dynasty collected

in the Palace Museum is well known to the public through CCTV's program: The Nation's Greatest Treasures. The

painting was regarded as a giant masterpiece in the blue-green landscape painting. Although it has gone through

nearly a thousand years，it is still brilliant as usual，the secret of which was that all the pigments were made of

gemstone minerals. According to the principle of physical chemistry，the chromatic mechanism of these pigments is

revealed one by one in this paper. This kind of crossover thinking could not only stimulate interest in learning，but

also could realize the perfect combination of modern science education and traditional culture.

Among spring-mass oscillators with nonlinear motions and two degrees of
freedom，the model confined

to horizontal frictionless plane has features of simple dynamic differential equations and separable variables. In

this study polar coordinates are used to construct the dynamic differential equations of the spring-mass oscillator

confined to horizontal frictionless plain. Variables related to radial motion are separated to form an individual dynamic

differential equation，which is researched by qualitative analysis and approximation theory due to its

nonlinear characteristic. Software MATLAB is used as a numerical method to simulate paths of the oscillator，verify

qualitative results and demonstrate the accuracy of approximate solutions in two specific situations.

The core result of Galileo's inclined plane experiment is the proportion
relation between distance and

the square of time，but the local inhomogeneity of the dip angle and friction coefficient leads to inhomogeneity of local

acceleration. In this paper，a simplified model including inhomogeneity of the dip angle and friction coefficient

is introduced. Numerical results show that this inhomogeneity not only induces random error but also leads to deviation

of the square relation between the distance and the time. It is further found that if the dip angle keeps unchanged

and the friction coefficient decreases，the ball should change from non-slip rolling to slip rolling，the deviation

degree of the square relation between the distance and the time would increase rather than decrease. This result，

although contrary to intuition，coincides with the result achieved in some corresponding researches on the history

of physics. These theoretical results are confirmed by our experiments. In order to exclude the random factors in

releasing the ball，an equipment is designed to release the ball with zero velocity. A more convenient method is also

carried out to measure the friction coefficient.

The string and pulley are often used as ideal models ( e.g.，Atwood machine with
a massless pulley

and a massless string) in textbooks to solve the dynamics problem of Atwood machine. The dynamical methods are

used to describe the motion of Atwood machine with a massive string. The effects on the system motion caused by

the mass of the pulley，the mass of the massive string and the initial position of the weight are analyzed. Furthermore，

the difference between the ideal model described in the text book and the motion of the Atwood machine under

the real conditions is discussed.

An improved experiment scheme about the verification of parallel axis theorem
for moment of inertia

is introduced. In the new scheme，the moment of inertia of the whole system is changed by changing the distance of

the steel pillars to the instrument rotational axis symmetrically. The variation of moment of inertia is made in a large

range and the symmetrical mass distribution is preserved. So that the relative error is significantly reduced and the

reliability of the verification of the theorem is substantially improved.

Aiming to the complex physical properties of liquid lead to the difficulty in
measuring its resistivity，

a new liquid-resistivity measuring device is designed in this paper. In order to collect the information of the object

under test effectively，the container is designed skillfully. Graphite electrode is applied innovatively to realize the

integration of the electrode and the container，which improves the measuring accuracy. The sensing technology is

used to collect voltage and current signals and transmitted the data to the MCU. The value of resistivity is displayed

on the LCD screen in real time after the operation of the MCU. With the advantages of quick and accurate measurement，

it has certain practical value in teaching and research.

Combining with lateral displacement amplification of Moiré fringe and
auto-collimation angle measuring

principle，based on the lateral Moiré fringe of auto-collimation angle measurement method，is analyzed by using

the shading principle of Moiré fringe displacement amplification effect. On the basis of the method to build the

principle of the optical path，the Moiré fringe signal is stable and can satisfy the measurement requirements. On the

basis of the system，data processing steps are simplified and dynamic measurement is realized. The quantitative calibration

experiment results show that the system resolution up to 10″，applying this method to the autocollimator can

significantly improve the resolution.