An object's weight, henceforth called "actual weight", is the downward force exerted upon it by a gravitational field. By contrast, an object's apparent weight is the (usually upward) force (the normal force, or reaction force), typically transmitted through the ground, that opposes the (usually downward) acceleration of a supported object, preventing it from falling.
It is apparent weight, rather than actual weight, that a weighing scale measures. Apparent weight is also responsible for our sensation of the weight of our own bodies. A greater apparent weight results in a heavier or greater sensation of our weight, and vice-versa.
An object's apparent weight is equal to its actual weight, unless:
The object has an acceleration, as in a lift, a rocket, or a rollercoaster. Some force other than the earth's gravity and the normal force is acting on the object. This may, for example, be buoyancy, centrifugal force due to the Earth's rotation, magnetic force, or the gravitational force of another astronomical body.
Apparent density (AD) This most important property is in a general sense the same as bulk density, i.e. it is the mass of a unit volume of powder, but the method and apparatus used to determine it need to be carefully specified if consistent results are to be obtained. The test normally specified-IS0 3923/1-is to allow the powder to emerge from a funnel through a specified orifice into a cylindrical cup of specified dimensions which overflows. The surplus is carefully removed by drawing a straight edge across the top of the cup, the powder in the cup then being weighed.
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