Edward J. Finn

On the notion of internal energy

The notion of internal energy at a level appropriate for students of the Introductory Physics Course (IPC) is examined. The methodology proposed offers a general frame for analysing practically any physical system or process in a system of particles, from thermal phenomena and phase transitions to chemical and nuclear reactions, including processes involving elementary particles. The role of interactions among particles in a system is emphasized. The notion of statistical equilibrium of a system is discussed in this context. Finally, two structure factors are introduced to show the relation between the kinetic, interaction and particle energies of a system in maintaining stable structures.

Linear Momentum Conservation in a Nonconservative Environment.

An experiment is described for the general physics laboratory where metal cylinders slide, with acceleration, down an inclined metal track and out onto a horizontal track. The apparatus is quite primitive and readily fabricated from easily available materials. After the coefficient of friction is calculated through energy considerations, the conservation of momentum and Q-value for elastic and inelastic collisions is investigated. The masses of the cylinders and various distances are the only measurements necessary. In this case where friction must not be ignored, the experiment has been found stimulating to beginning students and the results satisfactory, particularly when the collision is made totally inelastic (a capture reaction).

An Interactive Instruction Session in Ray Tracing

A set of interactive programs have been produced which assist a student to self-test himself for an understanding of ray-tracing techniques. The three programs discussed are concerned with plane mirror reflections and the images formed.