Centre-of-mass motion, the pauli principle and a generalized pseudometric

1973 ◽  
Vol 15 (1) ◽  
pp. 136-144 ◽  
Author(s):  
D. J. Ernst
Keyword(s):  
Pauli Principle ◽  
Mass Motion ◽  
Centre Of Mass

Associations between ground reaction force waveforms and sprint start performance

2019 ◽  
Vol 14 (5) ◽  
pp. 658-666 ◽  
Author(s):  
Steffi L Colyer ◽  
Philip Graham-Smith ◽  
Aki IT Salo
Keyword(s):  
Reaction Force ◽  
Statistical Parametric Mapping ◽  
Force Production ◽  
Mass Motion ◽  
Ground Reaction Forces ◽  
Centre Of Mass ◽  
Specific Training ◽  
Force Vector ◽  
Reaction Forces ◽  
External Power

Ground reaction forces produced on the blocks determine an athlete’s centre of mass motion during the sprint start, which is crucial to sprint performance. This study aimed to understand how force waveforms are associated with better sprint start performance. Fifty-seven sprinters (from junior to world elite) performed a series of block starts during which the ground reaction forces produced by the legs and arms were separately measured. Statistical parametric mapping (linear regression) revealed specific phases of these waveforms where forces were associated with average horizontal external power. Better performances were achieved by producing higher forces and directing the force vector more horizontally during the initial parts of the block phase (17–34% and 5–37%, respectively). During the mid-push (around the time of rear block exit: ∼54% of the block push), magnitudes of front block force differentiated performers, but orientation did not. Consequently, the ability to sustain high forces during the transition from bilateral to unilateral pushing was a performance-differentiating factor. Better athletes also exhibited a higher ratio of forces on the front block in the latter parts of unilateral pushing (81–92% of the block push), which seemed to allow these athletes to exit the blocks with lower centre of mass projection angles. Training should reflect these kinetic requirements, but also include technique-based aspects to increase both force production and orientation capacities. Specific training focused on enhancing anteroposterior force production during the transition between double- to single-leg propulsion could be beneficial for overall sprint start performance.

Centre-of-mass motion for a system of two unequal fragments

1979 ◽  
Vol 290 (3) ◽  
pp. 319-326 ◽  
Author(s):  
G. B�art ◽  
J. Deenen ◽  
G. Reidemeister
Keyword(s):  
Mass Motion ◽  
Centre Of Mass

One-atom laser with quantized centre-of-mass motion

1997 ◽  
Vol 40 (3) ◽  
pp. 263-268 ◽  
Author(s):  
M Löffler ◽  
G. M Meyer ◽  
H Walther
Keyword(s):  
Mass Motion ◽  
Centre Of Mass ◽  
Atom Laser

Static rivulet instabilities: varicose and sinuous modes

2018 ◽  
Vol 837 ◽  
pp. 819-838 ◽  
Author(s):  
J. B. Bostwick ◽  
P. H. Steen
Keyword(s):  
Static Stability ◽  
Linear Operators ◽  
Mass Motion ◽  
Hydrodynamic Equations ◽  
Centre Of Mass ◽  
Instability Mechanism ◽  
Inviscid Incompressible Fluid ◽  
Pressure Fields ◽  
Static Contact

A static rivulet is subject to disturbances in shape, velocity and pressure fields. Disturbances to interfacial shape accommodate a contact line that is either (i) fixed (pinned) or (ii) fully mobile (free) and preserves the static contact angle. The governing hydrodynamic equations for this inviscid, incompressible fluid are derived and then reduced to a functional eigenvalue problem on linear operators, which are parametrized by axial wavenumber and base-state volume. Solutions are decomposed according to their symmetry (varicose) or anti-symmetry (sinuous) about the vertical mid-plane. Dispersion relations are then computed. Static stability is obtained by setting growth rate to zero and recovers existing literature results. Critical growth rates and wavenumbers for the varicose and sinuous modes are reported. For the varicose mode, typical capillary break-up persists and the role of the liquid/solid interaction on the critical disturbance is illustrated. There exists a range of parameters for which the sinuous mode is the dominant instability mode. The sinuous instability mechanism is shown to correlate with horizontal centre-of-mass motion and illustrated using a toy model.

Variational approach to4He with separation of centre-of-mass motion

1973 ◽  
Vol 7 (14) ◽  
pp. 621-624 ◽  
Author(s):  
F. D. Pacati ◽  
S. Boffi
Keyword(s):  
Variational Approach ◽  
Mass Motion ◽  
Centre Of Mass

Variational treatment of the centre-of-mass motion

1985 ◽  
Vol 11 (2) ◽  
pp. 231-241 ◽  
Author(s):  
M Bouten ◽  
M C Bouten ◽  
T Cornelissens
Keyword(s):  
Mass Motion ◽  
Centre Of Mass ◽  
Variational Treatment

Perturbation theory for projected states

1973 ◽  
Vol 333 (1593) ◽  
pp. 157-170 ◽  
Keyword(s):  
Perturbation Theory ◽  
Quantum Systems ◽  
Model System ◽  
Basis Functions ◽  
Mass Motion ◽  
Centre Of Mass ◽  
Soluble Model ◽  
Standard Perturbation Theory

For quantum systems with a symmetry it is often convenient to start from a simple soluble model lacking the symmetry, and restore the symmetry by projection. If this is done for all eigenstates of the model system, one obtains an overcomplete set of basis functions, which is not suitable for standard perturbation theory. The paper develops a method by which one can do perturbation theory in this situation. The method is illustrated by application to the problem of the centre-of-mass motion of a nucleus, the symmetry being the translational and Galileo invariance.

Sign in / Sign up

Export Citation Format

Share Document