No abstract available

[en] The free kick problem is considered for three distinct cases: (i) no air drag or lift, (ii) linear drag, and (iii) linear drag and lift. For the first case, closed form formulas are derived for the initial velocities and angles. For the second case, two coupled algebraic equations written from the trajectory equation are given and solved numerically for the initial velocities and angles. For the third case, the equations of motion are solved approximately using perturbation techniques assuming the lift coefficient to be small compared to the drag coefficient. Because the time variable cannot be eliminated between the equations, four coupled sets of algebraic equations are solved numerically for the initial velocities and angles. All three results are compared with each other and the influences of drag and lift coefficients on the velocities and angles are outlined. (author)

[en] The review of works devoted to the determination of orbit and the investigation of the long-term motion of Halley's comet is presented. The first efforts to link some apparitions of the comet by one system of orbital elements as well as the attempts to recognize the past orbit by means of numerical integrations of the equations of the comet's motion are surveyed. The comparison of results obtained by different authors is discussed. 49 refs., 6 tabs. (author)

[en] In this paper, an energy pumping mechanism for locomotion is analysed. The pumping is accomplished by exerting forces perpendicular to the direction of motion. The paper attempts to demonstrate an interesting application of the classical mechanics to two sporting events: a person skating in a half pipe and a person travelling on a level surface on a skateboard. The equations of motion based on simplified mechanical models are derived using the Lagrange mechanics. The energy-pumping phenomenon is revealed through numerical simulations with simple pumping actions. The result presented in this paper can be used as an interesting class project in undergraduate mechanics or physics courses. It also motivates potential new applications of energy pumping in many engineering fields. (paper)

[en] Radial motion of photons through the Kerr spacetime is analyzed for both the black holes and the naked singularities. The regions allowed for radial motion are determined in terms of constants of motion of photons. Figures are drawn to exhibit the qualitatively different behaviour of these regions. It is shown that the qualitative behaviour is of the same character for all black holes, while it depends on the parameter α=a/M of the Kerr naked singularities. In the case of naked singularities a large vortex could be formed by photons in stable spherical orbits concentrated around the shell of zero-energy photons, located at the surface r=M. In the field of a Kerr black hole these spherical orbits may exist under the inner horizon only, and for zero-energy photons they cannot exist at all. (author)

[en] A PET-B01 positron emission tomographic imaging system is used for detecting head and heart of human being. The movements of the detector and its construction are detailed

[en] In this paper, free vibration analysis of annular Mindlin plates with free inner edge is presented. The discrete singular convolution method is used for discretization of equations of motion. Frequency values are presented illustrating the effect of boundary conditions, radius ratio, and thickness to radius ratio of the annular plate. Comparing results with those in the literature validates the present analysis. (author)

[en] On solving exactly relativistic equations of motion for the model molecule of two particles coupled elastically, it has been shown that in the framework of relativistic mechanics this system, and in general any closed system of interacting particles, is not inertial, In particular, the translational velocity of the mass center of such a system has, as a consequence of the nonlinearity of the equations, oscillatory components reflecting its internal transverse oscillations - it is a pulsed motion. This effect can in principle be seen in the time-of-flight experiments. The force constant of elastic coupling in the system, as seen by the observer at rest, is shown to decline with increase of the total momentum of the system

No abstract available

[en] It is known that a special case of the Lagrangian of two identical charged particles up to fourth order terms has been found. The object of this paper is to derive the generalized Lagrangian by a scheme which is somewhat different from the one known. On the other hand one can then proceed to give the Hamiltonian form up to the same order. (orig.)