What is the relationship between the amount of water and
object displaces and the weight of the object?
Who discovered this theory?
Great Question! You are asking about Archimedes Principle, which states:
An immersed object is buoyed up by a force equal to the weight of the fluid
If the object is floating, then the weight of the fluid (water) displaced
is equal to the weight of the object.
If the object is totally submerged, then the weight of the fluid displaced
is less than the weight of the object. The object has the same mass, but
weighs less in water due to this upward buoyant force acting on it.
For a good explanation of this, look into Paul Hewitt's Conceptual Physics
book. He has an excellent explanation of the phenomenon in simplified terms.
---Nathan A. Unterman
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Update: June 2012