Conceptual Physics, Global Edition

Don’t think of inertia as some kind of force. It isn’t! Inertia is a property of all matter to resist changes in motion. All matter possesses inertia.

The law of inertia. From Newton’s Principia (translated from the original Latin): Every object continues in a state of rest or of uniform speed in a straight line unless acted on by net external force.

A force, in the simplest sense, is a push or a pull. Its source may be gravitational, electrical, magnetic, or simply muscular effort.

When the net force on something is zero, we say that something is in mechanical equilibrium.4

Mass is a measure of inertia.

By momentum we mean inertia in motion. More specifically, momentum is defined as the product of the mass of an object and its velocity:

An object may store energy by virtue of its position. The energy that is stored and held in readiness is called potential energy (PE) because in the stored state it has the potential for doing work.

Law of conservation of energy: Energy cannot be created or destroyed; it can be transferred from one object to another or transformed from one form into another, but the total amount of energy never changes.