# What is inertia?

pohnpei397 | College Teacher | (Level 3) Distinguished Educator

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The term "inertia" refers to the fact that an object in motion will remain in motion (in the direction it is moving) AND an object at rest will remain at rest UNLESS these objects are acted upon by some outside force.

So, if something is not moving, you have to apply force on it to make it start moving.  If something is moving, it will continue to move in the same direction and at the same velocity unless some force acts on it.

The idea of inertia is quantifed in Isaac Newton's First Law of Motion.

neela | High School Teacher | (Level 3) Valedictorian

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The inertia is a property that keeps an object at its state.

When an external force acts an object, the property of inertia makes the object move in the direction of the force and not anywhere else.

A moving obect does not stop if no force acts on it. This is due to inertia.

The higher the velocity of an object, you need bigger force to stop it. So, the property of inertia has to do something with the velocity.

The higher the mass of an object, we need higher force to dicontinue its state of rest. So inertial is very well related with the mass of an object.

The qickness of displacement necessitates higher force to dicontinue the state of the object is also due to the inertia. So time and inertia is inter related.

Inertia , force, mass, velocity  and momentum, direction,distance, displacement and  time are all the elements interrelated.

krishna-agrawala | College Teacher | (Level 3) Valedictorian

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Inertia is a property of matter by virtue of which a body cannot move itself nor change the motion imparted to it. The idea of inertia is implicit in the Newton's first law of motion which states:

Every body continues to in its state of rest or of uniform motion in a straight line unless, acted upon by some external force.

This law is also known as law of inertia.

Numerically the inertia of a body may be equated with its mass. That id higher the mass of a body, higher is the its inertia or the resistance it offers to change in its state of rest or uniform motion.

fact-finder | (Level 3) Valedictorian

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Inertia is a tendency of all objects and matter in the universe to remain still, or, if moving, to continue moving in the same direction unless acted on by some outside force. This constitutes the first law of motion, formulated by the famed English mathematician and astronomer (a scientist specializing in the study of matter in outer space) Isaac Newton (1642-1727). To move an object that is at rest, enough external force must be applied to overcome the object's inertia. The larger a still object is, the more force is required to move it.

In his Philosophae Naturalis Principia Mathematica, published in 1687, Newton sets forth his three laws of motion. Newton's second law is that the force needed to move a still object is equal to its mass (total amount of matter in an object) times its acceleration (F = MA). The third law states that for every action there is an equal and opposite reaction.

Sources: Barnhart, Robert K. The American Heritage Dictionary of Science, p. 316; The Biographical Dictionary of Scientists: Physicists, pp. 119-21; Trefil, James. 1001 Things Everyone Should Know About Science, pp. 146-47.