Term information
In most physics textbooks, weight is the name given to the force on an object due to gravity.[1] However, some books use an operational definition, defining the weight of an object as the force measured by the operation of weighing it (that is, the force required to support it). Both definitions imply that weight is a force and that its value depends on the local gravitational field. For example, an object with a mass of one kilogram will have a weight of 9.8N on the surface of the Earth, about six times less on the Moon, and zero when floating freely far out in space away from all gravitational influence. The differences between the two definitions are discussed below. For example, they differ over the weight of an object in free fall, such as a falling apple or an astronaut in an orbiting spacecraft. In these cases, the operational definition implies the weight is zero, whereas the gravitational definition does not. An object's gravitational weight W numerically (i.e. as a purely scalar quantity) is the product of the mass m of the object and the magnitude of the local gravitational acceleration g:[2] Thus: W = m g. In the International System of Units (SI), the unit of measurement for weight is that of force, the newton. source: http://en.wikipedia.org/wiki/Weight