ISSN:0002-9505    

DOI:10.1119/1.11786

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

Several parameters concerning the performance of tennis rackets are examined both theoretically and experimentally. Information is obtained about the location of the center of percussion, the time a ball spends in contact with the strings, the period of oscillation of a tennis racket, and the coefficient of restitution of a tennis ball. From these data it may be possible to design a racket with improved playing characteristics.

ISSN:0002-9505    

DOI:10.1119/1.11787

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

We note that equations of state—by which we mean identical relations among the thermodynamic variables characterizing a system—are actually first‐order partial differential equations for a function which defines the thermodynamics of the system. Like the Hamilton‐Jacobi equation, such equations can be solved along trajectories given by Hamilton’s equations, the trajectories being quasistatic processes which obey the given equation of state. This gives rise to the notion of thermodynamic functions as infinitesimal generators of quasistatic processes, with a natural Poisson bracket formulation. This formulation of thermodynamic transformations is invariant under canonical coordinate transformations, just as classical mechanics is, which is to say that thermodynamics and classical mechanics have the same formal structure, namely a symplectic structure.

ISSN:0002-9505    

DOI:10.1119/1.11788

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

A simplified derivation of the equilibrium distribution functions is presented. The derivation proceeds from the change in the Helmholtz free energy when a particle is added to a system of fixed temperature, volume, and chemical potential. Besides its simplicity, this form of the derivation offers a clear view of the relationship between statistical mechanics and macroscopic thermodynamics.

ISSN:0002-9505    

DOI:10.1119/1.11789

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

Three examples ofspatialBose‐Einstein condensations in which the particles macroscopically occupy the lowest localized state of an inhomogeneous external potential are analyzed. The three cases are (a) a small potential well in a large box which causes a spectrum with a gap, (b) a harmonic oscillator potential, and (c) randomly sized trapping potentials caused by ’’impurities.’’ All three cases are two dimensional so that no Bose condensation occurs without the inhomogeneous potentials. An attempt is made to keep the treatments as mathematically simple as possible. A review of much of the literature of spatial Bose condensations is provided. The special problem of the form of the thermodynamic limit in an inhomogeneous potential is discussed for case (b). Numerical examples applying to monolayer4He adsorbed on a surface are treated.

ISSN:0002-9505    

DOI:10.1119/1.11790

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

The effect of the nonuniform irradiance across a laser beam on diffraction of the beam is investigated. Calculations of Fraunhofer diffraction by a circular aperture show the deviations which occur from the usual Airy disk for several relative spot and aperture sizes.

ISSN:0002-9505    

DOI:10.1119/1.11791

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

A low intensity laser light scattering laboratory exercise has been designed and introduced into the lower division physics course for biology students at the University of California, Santa Barbara. Students determine the diameter of micron‐sized latex spheres (simulated microbes) in water suspension. By using their own eyes as part of the measuring apparatus the students become personally involved in the experiment, which is relevant to their field of interest. Accuracies of 1%–2% are normal, and student response has been unusually positive.

ISSN:0002-9505    

DOI:10.1119/1.11792

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

Injection of a thin layer of solution at the boundary of a moving solvent is utilized to create a thin fluid sheet having an index of refraction greater than that of the surrounding medium. Conditions are such that light trapping is easily observed in the thin fluid sheet. Diffusion effects give rise to a concentration profile which is quadratic at the boundary. As a consequence of this quadratic dependence, an interesting hopping and refocusing of a trapped beam is observed as it traverses the fluid sheet. The observed phenomenon is readily modeled by use of the Navier Stokes equation and the diffusion equation.

ISSN:0002-9505    

DOI:10.1119/1.11793

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

The normal‐mode motions of a massive particle and a spring of non‐negligible mass to whose end it is attached are shown to be described by ’’nonorthogonal’’ displacement functions. Two equivalent methods of establishing an orthogonality relation — a specially defined inner product and application of the Riemann‐Stieltjes integral — are introduced. The results lead to the complete solution for the general motion of the spring‐plus‐particle system. This solution is applied to provide rigorous justification of the intuitive method that leads to the familiar rule (’’... add one‐third the mass of the spring ...’’) for obtaining the period of a particle oscillating at the end of a uniform spring whose non‐negligible mass is small in comparison. It is shown that the presence/absence of gravity is irrelevant to the general conclusions reached.

ISSN:0002-9505    

DOI:10.1119/1.11794

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

We describe a low budget experiment, using materials that are easily obtained, to measure the speed of sound with an error of less than 10%. The device consists of a Helmholtz resonator of cylindrical cross section (a standard 12‐oz beer bottle). The system is analogous to a mass vibrating on a spring. The resonant frequency is determined by the mass of the air plug located in and near the bottle neck and the spring constant associated with the elasticity of the air filling the remainder of the bottle. A simple procedure involving length measurements with a vernier caliper is outlined and a discussion of the approximations made in arriving at this procedure is presented.

ISSN:0002-9505    

DOI:10.1119/1.11898

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP