Explicit derivation of the relativistic mass-energy relation for internal kinetic and potential energies of a composite system

A straightforward derivation of relativistic expressions for the mechanical momentum, kinetic and total energies, and mass-energy equivalence (including potential energy) which does not require any knowledge of the energy-momentum relation for electromagnetic waves or consideration of elastic collisions, but is directly based on Newton's second law and Lorentz's transformations, is presented in this paper. The existence of an invariant force is shown to be important for the validity of the relativistic mechanics.

Geodesics without differential equations: general relativistic calculations for introductory modern physics classes

Introductory courses covering modem physics sometimes introduce some elementary ideas from general relativity, though the idea of a geodesic is generally limited to shortest Euclidean length on a curved surface of two spatial dimensions rather than extremal aging in spacetime. It is shown that Epstein charts provide a simple geometric picture of geodesics in one space and one time dimension and that for a hypothetical uniform gravitational field, geodesics are straight lines on a planar diagram. This means that the properties of geodesics in a uniform field can be calculated with only a knowledge of elementary geometry and trigonometry, thus making the calculation of some basic results of general relativity accessible to students even in an algebra-based survey course on physics.

Is corrections correcting? An examination of prisoner rehabilitation policy and practice in Queensland

This article provides an analysis of the policy and practice of prisoner rehabilitation in Queensland, and the extent to which they accord with international best practice. Actual practice was identified through interviews and written submissions from 20 ex-prisoners and 18 prisoner service providers (including two past staff members from Queensland prisons), as well as through an examination of reported judicial review decisions and Department of Corrective Services statistics. The results demonstrate that although the legislation and procedures suggest that a best practice system of prisoner rehabilitation exists in Queensland, there is a significant gulf between policy and practice. Far from being sufficiently prepared for release, Queensland prisoners are generally released directly from high security facilities into a community which they have great difficulty reintegrating into. The results suggest that the corrective services system in Queensland is not succeeding in fulfilling its primary purpose, 'correction', or in meeting its well-publicised goal of ensuring community safety.