In classical physics, particularly in mechanics, the inertia of a body is the property that determines its resistance to changes in its state of motion and is quantified by its inertial mass.
Inertia is described by the principle of dynamics, the principle of inertia (or Newton’s first law), which states that a body will remain in its state of rest or uniform rectilinear motion unless an external force intervenes to change that state.
The concept of inertia is related to several physical quantities, such as the moment of inertia, which quantifies the resistance to angular acceleration.
The term “inertia” is also used in a more general sense in non-mechanical contexts, where it means the resistance to change of some quantity over time; for example, in the context of qualitative thermodynamic considerations, it is relatively common to speak of “thermal inertia”, meaning the specific heat or heat capacity of a body by this generic term.
- The principle of inertia
- Moment of inertia