Force| Force |
In General > s.a. anomalous
acceleration; physical theories; physics
teaching; symplectic
structures.
* Idea: The time rate of change of momentum, or the spatial rate of
change of energy.
* History: There is a
tradition of trying to avoid the use of the concept (e.g., H Hertz, quantum
mechanics, general relativity below).
* Measurement: 2000,
The smallest measured forces are femtonewton forces between DNA molecules [@
news
pn(00)may];
2006, Measurement of attonewton forces [@ Arlett et al NanoLett(06)] and practical
piconewton force measurement for cell biology [@ news pn(06)dec].
@ General references: Jammer 57.
@ In special relativity: Coleman NCB(06)
[and gravity]; Kholmetskii & Yarman EJP(07)
[resolution of apparent paradoxes].
Types and Examples > s.a. Centrifugal
Force;
newtonian gravity [tidal]; Lorentz Force; self-force.
* Pseudoforces: Fictitious
forces that arise when one uses non-inertial frames of reference; Examples
are the Coriolis force (velocity-dependent),
and, in Einstein's view, the force of gravity.
@ Special forces: Dolgov PRP(99) [long-range]; Lynden-Bell Obs(00)ap [preserving
the magnitude of a vector]; Vallejo mp/06 [inertial].
In Curved Spacetime / General Relativity > s.a. geodesic [deviation];
orbits of test bodies and gravitating
objects.
* Idea: Given a world-line with velocity 
a and curvature/acceleration
m
m a, the force on it is defined by
Fa := m mm a
= m–1 pm m
pm ;
This force cannot be given as a vector field and is strongly observer-dependent,
so one often tries to avoid its use.
* Maximum force or power: The
principle according to which no force can exceed Fmax =
c4/4G = 3.0 
1043 N,
and no power can exceed Pmax =
c5/4G = 9.1 1051 W;
The values can be obtained easily from Planck units (up to the factor 4), but
physically force or power coresponds to momentum flow, and the maximum can
be attained only through horizons.
@ General references: De Felice MNRAS(91);
Qadir & Sharif NCB(92)gq/07;
Qadir & Zafarullah
NCB(96); Arminjon AoM(96)gq/06 [and
Newton's second law].
@ Inertial: Prasanna gq/01;
Foertsch
et al CQG(03)gq [photon
surfaces]; Jonsson CQG(06)-a0708 [general
formalism, and optical geometry].
@ Centrifugal: Prasanna gq/01/CQG
[and Coriolis]; Hasse & Perlick GRG(02)gq/01 [and lensing].
@ Related topics: Semerák NCB(95)
[decomposition];
Price GRG(04)gq [normal
to
4-velocity]; Schiller IJTP(05)phy/06 [general
relativity
from maximum power or force]; > s.a. matter
phenomenology [maximum tension].
In Quantum Theory > s.a. interaction.
@ References: Mullin & Blaylock AJP(03)dec
[particle statistics and "exchange
force"].
main page – abbreviations – journals – comments – other
sites – acknowledgements
send feedback and suggestions to bombelli at olemiss.edu – modified 29
jun
2009