# inertia

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Related to Principle of inertia: Newton's second law

## inertia

(ĭnûr`shə), in physics, the resistance of a body to any alteration in its state of motion**motion,**

the change of position of one body with respect to another. The rate of change is the speed of the body. If the direction of motion is also given, then the velocity of the body is determined; velocity is a vector quantity, having both magnitude and direction, while speed

**.....**Click the link for more information. , i.e., the resistance of a body at rest to being set in motion or of a body in motion to any change of speed or change in direction of motion. Inertia is a property common to all matter. This property was first observed by Galileo and restated by Newton as his first law of motion, sometimes called the law of inertia. Newton's second law of motion states that the external force required to affect the motion of a body is proportional to that acceleration. The constant of proportionality is known as the mass

**mass,**

in physics, the quantity of matter in a body regardless of its volume or of any forces acting on it. The term should not be confused with weight, which is the measure of the force of gravity (see gravitation) acting on a body.

**.....**Click the link for more information. , which is the numerical value of the inertia; the greater the inertia of a body, the less is its acceleration for a given applied force.

## Inertia

That property of matter which manifests itself as a resistance to any change in the motion of a body. Thus when no external force is acting, a body at rest remains at rest and a body in motion continues moving in a straight line with a uniform speed (Newton's first law of motion). The mass of a body is a measure of its inertia. *See* Mass

## inertia

(i-**ner**-shă) The property of a body by which it resists change in its velocity. It is inertia that causes a body to continue in a state of rest or of uniform motion in a straight line (see Newton's laws of motion). The force required to give a specific acceleration to a body depends directly on its inertia. It is through the property of inertia that the concept of the mass of a body (its

*inertial mass*) arises.

## Inertia

in mechanics, a property of material bodies that is reflected in the first and second laws of mechanics. When there are no external influences (forces) acting on a body or when they are mutually balanced, inertia is manifested in the fact that the body maintains unchanged its state of motion or rest with respect to the so-called inertial frame of reference. If, however, an unbalanced system of forces acts on the body, then the property of inertia is manifested in the fact that a change in the body’s state of rest or motion, that is, a change in the velocities of its points, takes place gradually and not instantaneously. Here, the greater the inertia of the body the more slowly the motion changes. The mass of a body is the measure of its inertia.

The term “inertia” is still used with respect to various instruments; the inertia of an instrument is its property of displaying readings with a certain delay.

S. M. TARG

## inertia

[i′nər·shə]## inertia

*Physics*

**a.**the tendency of a body to preserve its state of rest or uniform motion unless acted upon by an external force

**b.**an analogous property of other physical quantities that resist change