inertiamassa

Inertiamassa, often referred to as inertial mass, is a property of matter that quantifies its resistance to changes in motion. In Newtonian mechanics, the acceleration a of a body under the action of a net force F is given by a = F/m, where m denotes the inertiamassa. This means that, for a given force, objects with larger inertiamassa experience smaller accelerations, and the proportionality is the same in all directions within an inertial frame.

Inertiamassa is closely related to, but conceptually distinct from, gravitational mass. The gravitational force on a body in a gravitational field is F_g = m_g g, with m_g the gravitational mass and g the field strength. The equivalence principle asserts that inertiamassa and gravitational mass are equal (within experimental uncertainty), so bodies accelerate identically in a given gravitational field regardless of their composition. This principle has been tested extensively since the 19th century, with modern experiments achieving precision better than about one part in 10^13.

In modern physics, the idea of inertiamassa is embedded in the framework of relativity. In special relativity, the relation between force and acceleration becomes velocity-dependent, while in general relativity the experience of inertia is tied to the geometry of spacetime. Rest mass (the invariant mass) is distinguished from the concept of relativistic mass, which increases with speed in some formulations. In the Standard Model, many elementary particles acquire mass through interactions with the Higgs field, though most of the mass of composite objects arises from internal binding energy rather to the Higgs mechanism alone.