# inertia

inertia
/in err"sheuh, i nerr"-/, n.
1. inertness, esp. with regard to effort, motion, action, and the like; inactivity; sluggishness.
2. Physics.
a. the property of matter by which it retains its state of rest or its velocity along a straight line so long as it is not acted upon by an external force.
b. an analogous property of a force: electric inertia.
3. Med. lack of activity, esp. as applied to a uterus during childbirth when its contractions have decreased or stopped.
[1705-15; < L: lack of skill, slothfulness. See INERT, -IA]
Syn. 1. torpor, inaction, laziness.

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Inherent property of a body that makes it oppose any force that would cause a change in its motion.

A body at rest and a body in motion both oppose forces that might cause acceleration. The inertia of a body can be measured by its mass, which governs its resistance to the action of a force, or by its moment of inertia about a specified axis, which measures its resistance to the action of a torque about the same axis.

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property of a body by virtue of which it opposes any agency that attempts to put it in motion or, if it is moving, to change the magnitude or direction of its velocity. Inertia is a passive property and does not enable a body to do anything except oppose such active agents as forces and torques. A moving body keeps moving not because of its inertia but only because of the absence of a force to slow it down, change its course, or speed it up.

There are two numerical measures of the inertia of a body: its mass, which governs its resistance to the action of a force, and its moment of inertia (inertia, moment of) about a specified axis, which measures its resistance to the action of a torque about the same axis. See Newton's laws of motion.

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Universalium. 2010.

Synonyms:

### Look at other dictionaries:

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• inertia — 1713, introduced as a term in physics 17c. by German astronomer and physician Johann Kepler (1571 1630), from L. inertia unskillfulness, idleness, from iners (gen. inertis) unskilled, inactive; see INERT (Cf. inert). Used in Modern Latin by… …   Etymology dictionary

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• Inertĭa — (lat.), Trägheit, Beharrungsvermögen …   Meyers Großes Konversations-Lexikon

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