Vis inertiae

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.
Inertness; inactivity.

See also: Vis, Vis

References in periodicals archive ?
Thus, the vis inertiae can be the source of an impressed force exerted upon another body.
In Definition 3 of the Principia, Newton very strikingly and paradoxically describes inertia as vis inertiae, the force of inertia, and identifies this force with materiae vis insita, translated here as "inherent force of matter.
Even though the word "perseverance" (perseverare) ordinarily connotes activity and though in Definition 4 Newton writes that "a body perseveres in any new state solely by the force of inertia," nevertheless, the vis inertiae operates only (solommundo) during a body's change of state in response to an impressed force.
As spoken of by contemporary physicists, inertial or fictitious forces, though related to Newton's vis inertiae, do not have exactly the same meaning, though for both, a body's inertia is acknowledged as a true source of the phenomena under consideration.
69) In the Opticks, first published in 1704, Newton also makes it clear that the vis inertiae is not an agency within a body that causes it to move or rest:
The passivity of the vis inertiae precludes it from being an agency of a body's own uniform rectilinear motion or rest, for that would make it an active principle, which for Newton is a kind of efficient cause.
77) As such, inertia would be an inherent principle by which a body acts in the characteristic ways that Newton ascribes to the vis inertiae, for everything acts according to its form.
So considered, inertial motion would be consistent with Newton's claim that the vis inertiae of a body does not operate as a continuous mover that keeps a body in uniform rectilinear motion.
90) Consequently, just as rest was not considered an activity, so too persevering in uniform rectilinear motion was not considered an activity, which is one reason that on Newton's account the vis inertiae is inactive in such motion.