Lenka Czudková

The pendulum: a stumbling block of secondary school mechanics

In this article we refer to the somewhat surprising fact that questions connected with the mechanics of such popular physical models as the simple and conical pendulum seem to be difficult not only for secondary school students but even for those taking introductory university courses in physics. Two tests concerning both the simple pendulum and the conical pendulum were examined by groups of 50 students. We give a brief analysis of their unsatisfactory results as well as a correct presentation of the problem at the secondary school level.

Physics in a lift and on a turntable

This paper presents a method for the elementary explanation of Newtons second law for a mass particle moving in non-inertial reference frames. The concept of inertial forces is introduced on the kinematical basis as the exceptional consequence of the mutual motion of reference frames. The inertial forces are interpreted as the fictive ones, having no support in the standard formulation of Newtons laws.

Variational non-holonomic systems in physics

In this paper conditions of variationality for mechanical systems subjected to non‐holonomic constraints (constraint Helmholtz conditions), recently obtained by Krupkova and Musilova, are examined in some concrete physical situations. Influence of the choice of constraints on the variationality is studied and corresponding constraint forces are obtained.

Non-holonomic constraint forces in field theory in physics

We study non-holonomic constraint forces using the geometrical theory of non-holonomic constrained systems on fibered manifolds with n-dimensional base, n > 1, and their prolongations proposed by Krupkova. Properties of so-called Chetaev type constraint forces, that arise as a result of this geometrical theory, are illustrated on concrete physical example from continuum mechanics (more precisely, from elasticity theory). By means of this example the geometrical as well as physical aspects of the theory are analysed. We sketch also the quite general approach to a problem of non-holonomic constraint forces.