- published: 09 Apr 2015
- views: 1557630
In physics, mass (from Greek μᾶζα "barley cake, lump (of dough)"), more specifically inertial mass, can be defined as a quantitative measure of an object's resistance to the change of its speed. In addition to this, gravitational mass can be described as a measure of magnitude of the gravitational force which is
when interacting with a second object. The SI unit of mass is the kilogram (kg).
In everyday usage, mass is often referred to as weight, the units of which are often taken to be kilograms (for instance, a person may state that their weight is 75 kg). In scientific use, however, the term weight refers to a different, yet related, property of matter. Weight is the gravitational force acting on a given body—which differs depending on the gravitational pull of the opposing body (e.g. a person's weight on Earth vs on the Moon) — while mass is an intrinsic property of that body that never changes. In other words, an object's weight depends on its environment, while its mass does not. On the surface of the Earth, an object with a mass of 50 kilograms weighs 491 Newtons; on the surface of the Moon, the same object still has a mass of 50 kilograms but weighs only 81.5 Newtons. Restated in mathematical terms, on the surface of the Earth, the weight W of an object is related to its mass m by W = mg, where g is the Earth's gravitational field strength, equal to about 9.81 m/s2.