Ping-Pong vacuum cannons, potato guns, and compressed air cannons are popular and dramatic demonstrations for lecture and lab. Students enjoy them for the spectacle, but they can also be used effectively to teach physics. Recently we have used a student-built compressed air cannon as a laboratory activity to investigate impulse, conservation of…

Describes how to construct a simple bimetallic element and pointer for an overhead projector. The device can be used to demonstrate operation of bimetallic elements. (RH)

Describes a micromanipulator that is inexpensive, simple to build, rugged, and capable of several modes of operation beyond those of other types. It can, for example, be used with its controls quite remote from the tool holder and microscope or be controlled by computer. (JN)

A homemade device for testing particle scattering is described. Also described are experiments in zero gravity conducted in free fall in the cargo space of an airplane belonging to the National Aeronautics and Space Administration. (JN)

The preparation and performance of a graphite (silver/copper sulfide) electrode is described. This rod, extracted from a used dry cell, is an acceptable substitute for ion-selective electrodes after it has been cleaned by abrasion followed by an overnight treatment with hydrochloric acid. (JN)