forceForce2026-08-22 18:13:402026-08-22 18:13:40Definitionmodernize to wiki's entry which is way better% this is the default PhysicsLibrary preamble. as your knowledge
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% Modernized from Louis Brand, Vectorial Mechanics (1930), Chapter II, Article 21.
% Public domain in the United States.
\section*{Force}
A force is a vector quantity that represents a mechanical interaction acting
on a body. In particle mechanics a force is specified by its magnitude and
direction together with the particle on which it acts. For an extended body,
the point of application or, for rigid-body statics, the line of action is also
important.
We denote a force by a bold symbol such as $F$ and its magnitude by
\[
F=\lVert\mathbf F\rVert.
\]
In SI units force is measured in newtons (N), with
\[
1\ \mathrm{N}=1\ \mathrm{kg\,m/s^2}.
\]
\subsection*{Measurement}
Brand motivated force measurement with a calibrated spring balance. The modern
version is the same in spirit: a force sensor is calibrated against known
standards and produces a repeatable reading related to force magnitude. The
essential point for statics is that force is not merely a scalar reading; it
has direction and acts on a specified body.
\subsection*{Force as a sliding vector for a rigid body}
At this stage it is safest to regard a force on an extended body as a vector
with a point of application. Later, the transmissibility principle shows that
for the \emph{external equilibrium and motion of an ideal rigid body}, a force
may be shifted anywhere along its line of action without changing its external
mechanical effect. This does not imply that the internal stress state of a
deformable body is unchanged.
\section*{Modern notation references}
The notation and terminology in this modernized article follow standard
present-day mechanics usage, particularly:
\begin{enumerate}
\item J. R. Taylor, \emph{Classical Mechanics}, University Science Books, 2005.
\item D. Kleppner and R. Kolenkow, \emph{An Introduction to Mechanics}, 2nd ed., Cambridge University Press, 2014.
\item R. C. Hibbeler, \emph{Engineering Mechanics: Statics}, 14th ed., Pearson, 2016.
\end{enumerate}
\section*{Source}
This article is a modernized restatement of the corresponding article in
Louis Brand, \emph{Vectorial Mechanics}, John Wiley \& Sons, New York, 1930,
Chapter II, ``Statics: Fundamental Principles.'' The original 1930 edition is
the source basis and is in the public \PMlinkescapetext{domain} in the United States.