Harold A. Daw

Two Air-Supported Devices for Physics Laboratories and for Physics Demonstrations

Two air-supported devices are described. One is an air-bearing gyroscope and the other a classical “nuclear” magnetic resonance apparatus using an air-bearing gyroscope.

A Two-Dimensional Air Table

The construction of a two-dimensional air table is described. This is an extention of the Neher-Leighton one-dimensional air trough to two dimension. The air cushion is provided by a perforated surface placed over an air-distribution manifold. The pucks consist of solid glass disks. A special wall keeps the energy loss from the system small. The conservation laws of linear and angular momentum can easily be studied, as can the general behavior of a two-dimensional gas.

Coriolis lecture demonstration

This article describes a mechanical system for viewing motion in a rotating reference frame and in particular under a pure Coriolis acceleration. It also discusses how this motion may be made visible to a large audience by using a TV camera in the rotating frame and projecting the motion in the rotating frame on a screen. In addition, the article discusses the theory involved in producing a pure Coriolis acceleration.

A two‐dimensional flame table

A two‐dimensional flame table was constructed for visually demonstrating acoustical modes in a cavity. This flame table is an extension of the one‐dimensional flame tube or Rubens flame tube apparatus. Photographs of some of the lower‐order modes on rectangular box and cylindrical box flame table cavities are included.

The normal mode structure on the two‐dimensional flame table

The flame structure on a two‐dimensional flame table is analyzed in terms of the eigenfunctions of the applicable geometry. The mathematical solutions to the pictures reproduced in an earlier article [H. A. Daw, Am. J. Phys. 55, 733 (1987)] are given. In particular, the flames are found to be strongest at the zeros of the eigenfunctions for the pressure amplitude and therefore follow ‘‘normal operation’’ [G. Ficken and F. C. Stephenson, Phys. Teach. 17, 306 (1979)]. ‘‘Reversal’’ is also clearly observed on the flame table.

The New Mexico State University motion room

This article describes the construction and operation of a totally enclosed motion room capable of carrying four students. The room is used for studying motion in a rotating frame. The rotation rate can be varied from 0 to above 20 rpm. Unique features of this motion room are the 60‐in. searchlight frame used for the mount and electrical connections and the two cattle watering troughs used for the motion room proper. The room, built a number of years ago, has not previously been described in the literature.

Water flow demonstration in the rotating frame

This article deals with fluid flow in a rotating coordinate frame and how to make the characteristics of the flow visible to lecture‐demonstration‐size audiences. This is a sequel to an earlier article [H. A. Daw, Am. J. Phys. 55, 1010–1014 (1987)] dealing with a rolling ball in the rotating frame. Basically, the same apparatus is used. The path of the fluid flow in a uniformly rotating system in two dimensions is made visible using food coloring, and observation is made by using a video camera. A simple derivation of the flow path is given. The article concludes with the description of a demonstration showing the formation of whirlpools.