Sunday, August 7, 2011

Actual weight and apparent weight

Buoyant force makes thing seem to be lighter.

The weight of an object in air is its actual weight
The weight measured when the object is immersed in a fluid is its apparent weight.
The buoyant force is equal to the apparent loss in weight.
The object displaces a volume of water.
The bigger the volume of the object immersed, the bigger the volume of the liquid displaced.
•  Volume of liquid displaced  = volume of the submerged part of the  object.

Work example :


An object weights 2.5 N.  When it is fully submerged in a liquid, its apparent weight is 2.2 N.

(a) What is the buoyant  force on the object in  water?
 Tips : Fb= Wc- Wa

(b) What is the weight of water displaced by the object?
 Tips : Weight , W = mass, m x gravitational force, g
In SPM take g = 10 Nkg-1

(c) Determine the volume  of water displaced by  the object.
[density of water = 1000 kgm-3]
 Tips : Density = mass / volume 

(d) What is the volume of the object?
 Tips : Volume of liquid displaced  = volume of the submerged part of the  object.  

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