12 The Soap Spiral
Lower a compressed slinky into a soap solution, pull it out and straighten it. A soap film is formed between the turns of the slinky. If you break the integrity of the film, the front of the film will begin to move. Explain this phenomenon and investigate the movement of the front of the soap film.
  •  Vorführexperimente, Videos
  • Playing with bubbles and slinky toy - so much fun for kids and adults too!

    another demonstration video

  • short phenomenom demonstation

    another demonstation video

  •  Wissenschaftliche Artikel
  • Instabilities and Solitons in Minimal Strips

    We show that highly twisted minimal strips can undergo a nonsingular transition, unlike the singular transitions seen in the Möbius strip and the catenoid. If the strip is nonorientable, this transition is topologically frustrated, and the resulting surface contains a helicoidal defect. Demonstrations with soap films confirm these results and show how the position of the defect can be controlled through boundary deformation.

  • Longitudinal standing waves on a vertically suspended slinky

    The vertically suspended slinky is a system where variable tension, and variable mass density, combine to produce a simple solution for the longitudinal normal modes. The time taken for a longitudinal wave to traverse a single turn of the slinky is found to be constant for a variety of slinky configurations. For the freely suspended slinky this constant traverse time yields standing wave frequencies that depend only on the length of the hanging slinky and not on the material, radius, or stiffness of the slinky. Data, obtained by students in a laboratory setting, are presented to illustrate the application of these results.

  • Minimal surfaces bounded by elastic lines

    In mathematics, the classical Plateau problem consists of finding the surface of least area that spans a given rigid boundary curve. A physical realization of the problem is obtained by dipping a stiff wire frame of some given shape in soapy water and then removing it; the shape of the spanning soap film is a solution to the Plateau problem. But what happens if a soap film spans a loop of inextensible but flexible wire?

  • Physics of Soap Films

    Soap films constituting from two surfactant monolayers sandwiching a thin layer of water are investigated. The structure of such films is not static because thermal fluctuations induce corrugations on the monolayers.

  • Problem solving with soap films: Part II

    It was shown in the previous article that it was possible to solve some two dimensional minimization problems by building an analogue system consisting of plates and pins and dipping the system into soap solution. The soap film produced between the plates when the system is withdrawn from the soap solution has the property that its length is minimized once the soap film has reached thermodynamic equilibrium. This article extends the method in order to solve problems requiring the determination of the minimum surface area bounded by lines in three dimensions. The specific problems examined have been chosen that the boundaries have a high degree of symmetry.

  • Shapes of embedded minimal surfaces

    It has been known that the right mathematical model for a soap film is a minimal surface: the soap film is in a state of minimum energy when it covers the least possible amount of area. There are several other fields where minimal surfaces are actively used in understanding the shapes of physical phenomena. The authors discuss here the answer to the following questions: What are the possible shapes of embedded minimal surfaces in R3, and why?

  • The Geometry of Soap Films and Soap Bubbles

    The possible configurations they can form are governed by a few elementary rules that have been known for more than a century. A new mathematical model provides a sound basis for those rules.

  • The Helicoid versus the Catenoid: Geometrically Induced Bifurcations

    The minimal surfaces bounded by a frame formed of a double helix and two horizontal rods are studied. The vibration equation shows that the helicoid is the stable surface when its winding number is small. The catenoid is locally isometric to the helicoid so that their vibration spectra are strongly related. While the catenoid is known to undergo a discontinuous transition to two disks, the helicoid is shown to become unstable through a continuous transition to a ribbon-shaped surface obtained experimentally, numerically, and analytically in the limit of infinite height. The normal forms of the bifurcations confirm the analysis.

  • The Physics of the Tumbling Spring

    Study of the dynamics of wave motion along a slinky