Conceptual Physics 12th Edition - Paul G. Hewitt Chapter 2

Inertia

The property of things to resist changes in motion.

Newton's first law of motion (the law of inertia)

Every object continues in a state of rest or of uniform speed in a straight line unless acted on by a nonzero net force.

Force

In the simplest sense, a push or pull.

Net force

The vector sum of forces that act on an object.

Vector

An arrow drawn to scale used to represent a vector quantity.

Vector quantity

A quantity that has both magnitude and direction, such as a force.

Scalar quantity

A quantity that has magnitude but not direction, such as mass and volume.

Resultant

The net result of a combination of two or more vectors.

Mechanical equilibrium

The state of an object or system of objects for which there are no changes in motion. In accord with Newton's first law, if an object is at rest, the state of rest persists. If an object is moving, its motion continues without change.

Equilibrium rule

For any object or system of objects in equilibrium, the sum of the forces acting equals zero.