Inertia
ih-NER-shuh
/ɪˈnɜːrʃə/
The tendency of an object to resist any change in its state of motion (or rest).
Inertia is directly proportional to an object's mass. A more massive object has more inertia and is harder to start moving or stop once it's moving.
The story behind the word. "Inertia" comes from the Latin "inertia," meaning "idleness, inactivity, sluggishness." This is derived from "iners," which means "unskilled, inactive, idle." The connection is clear: an object exhibiting inertia is "idle" or "inactive" in terms of changing its own state of motion.
Word relationships
- resistance: "Resistance" is a general opposition, while "inertia" specifically refers to resistance to changes in motion.
- sluggishness: Implies slowness or inactivity, which can be a consequence of high inertia but isn't the property itself.
- momentum (in a metaphorical sense): While not a direct antonym in physics, metaphorically, "momentum" implies continued progress, opposite to "inertia" as resistance to change.
- dynamism: Active, energetic, opposite to the passive resistance of inertia.
Commonly confused with
- Apathy: Apathy is a lack of interest or emotion; inertia is a physical property or a metaphorical resistance to change.
Word family
- inert (adjective): Lacking the ability or strength to move.
- inertially (adverb): In an inert manner (rare).
Collocations
- thermal inertia
- moment of inertia
- overcome inertia
- rotational inertia
- political inertia
Idioms & expressions
- overcome inertia
Example sentences
- "Due to its sheer mass, a supertanker has enormous inertia, making it difficult to stop or change direction quickly." Explaining a concept in physics.
- "A body at rest tends to remain at rest, and a body in motion tends to remain in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This is the principle of inertia." From a scientific principle. (Newton's First Law of Motion)
Memory hook
INERTIA makes an INERT object stay put, or keep moving. Inert Inactivity
When not to use
While "inertia" can be used metaphorically (e.g., "bureaucratic inertia"), be mindful of its precise scientific meaning when discussing physics.
Fun facts
- Newton's First Law of Motion is often called the Law of Inertia.
- The feeling of being pushed back into your seat when a car accelerates is due to your body's inertia.
Explore more words
propel, equilibrium, Properties, stability, accretion, perpetual
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