Momentum vs. Inertia — What's the Difference?

In Newtonian mechanics, linear momentum, translational momentum, or simply momentum (pl. momenta) is the product of the mass and velocity of an object.

Inertia is the resistance of any physical object to any change in its velocity. This includes changes to the object's speed, or direction of motion.

Symbol p(Physics) A quantity used to measure the motion of a body, equal to the product of the body's mass and its velocity. Also called linear momentum.

A tendency to do nothing or to remain unchanged

The force or energy exhibited by a moving body

A property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force

The driving force or advancing strength of a development or course of events

(Physics) The tendency of a body at rest to remain at rest or of a body in straight line motion to stay in motion in a straight line unless acted on by an outside force; the resistance of a body to changes in momentum.

(Philosophy) An essential or constituent element; a moment.

Resistance or disinclination to motion, action, or change

(physics) Of a body in motion: the tendency of a body to maintain its inertial motion; the product of its mass and velocity, or the vector sum of the products of its masses and velocities.

The property of a body that resists any change to its uniform motion; equivalent to its mass.

The impetus, either of a body in motion, or of an idea or course of events; a moment.

(figuratively) In a person, unwillingness to take action.

The quantity of motion in a moving body, being always proportioned to the quantity of matter multiplied by the velocity; impetus.

(medicine) Lack of activity; sluggishness; said especially of the uterus, when, in labour, its contractions have nearly or wholly ceased.

Essential element, or constituent element.

That property of matter by which it tends when at rest to remain so, and when in motion to continue in motion, and in the same straight line or direction, unless acted on by some external force; - sometimes called vis inertiæ. The inertia of a body is proportional to its mass.

A property of an activity or course of events, viewed as analogous to forward motion or to physical momentum (def. 1), such that the activity is believed to be able to continue moving forward without further application of force or effort; - often used to describe an increase in the acquisition of public support for a purpose; as, as, the petition drive gained momentum when it was mentioned in the newspapers.

Inertness; indisposition to motion, exertion, or action; lack of energy; sluggishness.

An impelling force or strength;

Lack of activity; sluggishness; - said especially of the uterus, when, in labor, its contractions have nearly or wholly ceased.

The product of a body's mass and its velocity;

A disposition to remain inactive or inert;

(physics) the tendency of a body to maintain is state of rest or uniform motion unless acted upon by an external force