Page "Mass" Paragraph 4

In everyday usage, mass is referred to as " weight ", the units of which may be pounds or kilograms ( for instance, a person's weight may be stated as 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