Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Archimedes Principle
Name: Emily
Status: student
Age: 13
Location: N/A
Country: N/A
Date: 1999 

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 it displaces.

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

Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory