2. (Law)
(a) Physical force.
(b) Moral power.
{Principle of vis viva} (Mech.), the principle that the
difference between the aggregate work of the accelerating
forces of a system and that of the retarding forces is
equal to one half the vis viva accumulated or lost in the
system while the work is being done.
{Vis impressa} [L.] (Mech.), force exerted, as in moving a
body, or changing the direction of its motion; impressed
force.
{Vis inerti[ae]}. [L.]
(a) The resistance of matter, as when a body at rest is
set in motion, or a body in motion is brought to rest,
or has its motion changed, either in direction or in
velocity.
(b) Inertness; inactivity.
Note: Vis interti[ae] and inertia are not strictly
synonymous. The former implies the resistance itself
which is given, while the latter implies merely the
property by which it is given.
{Vis mortua} [L.] (Mech.), dead force; force doing no active
work, but only producing pressure.
{Vis vit[ae]}, or {Vis vitalis} [L.] (Physiol.), vital force.
{Vis viva} [L.] (Mech.), living force; the force of a body
moving against resistance, or doing work, in distinction
from vis mortua, or dead force; the kinetic energy of a
moving body; the capacity of a moving body to do work by
reason of its being in motion. See {Kinetic energy}, in
the Note under {Energy}. The term vis viva is not usually
understood to include that part of the kinetic energy of
the body which is due to the vibrations of its molecules.