Apparatus Competition

2007 AAPT Summer Meeting

Greensboro, NC


A simple apparatus for use in determining the diameter and location of a hidden circular cavity


A. James Mallmann

Department of Physics and Chemistry

Milwaukee School of Engineering

1925 North Broadway

Milwaukee, WI   53202-3109





This simple, inexpensive apparatus, easily constructed using three sheets of fiberboard, is designed to challenge students to accomplish two goals:

       The easier goal is to determine the diameter of a hidden circular cavity.

       The more challenging goal is to determine the location of the center of the hidden circular cavity.


Construction of Apparatus:

The three-layer sandwich of one-eighth or one-fourth-inch                                                              

thick fiberboard sheets shown here

is fabricated by gluing together three identically shaped sheets shown in the lower portion of the photo.

   The apparatus will include a single sheet of the fiberboard for use in determining the density of the material.


Use of Apparatus:


This apparatus will be used by students for the first time during the fall of 2007. We believe that the use of the apparatus by students will have several advantages:




Equipment and costs required to construct apparatus:



Part number



Lumberyard or hardware store



Ordinary carpentry tools








Total Cost