Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page Visit Our Archives Ask A Question How To Ask A Question Question of the Week NEWTON Teachers Our Expert Scientists Volunteer at NEWTON! Referencing NEWTON Frequently Asked Questions About Ask A Scientist About NEWTON Education At Argonne Liquid Paraboloid

Name: Nate
Status: educator
Grade: 9-12
Location: IL
Country: USA
Date: Winter 2012-2013


Question:
We have a thin, wide, tall, parallelepiped that is 1/3 filled with a fluid (colored water). When placed on a rotating platform, it forms a section of a paraboloid. This is a similar to how some telescope mirrors are manufactured. Looking at the centripetal force equation, F=4*pi*pi*r/T*T, the force is proportional to the radius, not the radius squared. So why do we have a paraboloid?

Replies:
Hi Nate,

The behavior you describe is indicative of fluid dynamics. Flow of liquids in a tube is unique and largely dynamic pressure driven. You are probably observing centripetal force, dynamic pressure and adhesion(at the interface).

The mathematics are chaotic(dynamic) rather than straightforward. The reference below is concerning development of an algorithm. In the thought analysis, the author presents(by figure) and gives examples of the very phenomenon you observe. His analysis is the part about mid-way through using an inverted T tube. His conclusion is that the force is proportional to both, r and v squared.

http://www.fractalforums.com/let's-collaborate-on-something!/developing-fractal-algorithm-for-fluid-dynamics/?PHPSESSID=6997a99a02090ebaeea945c88aeaa7cf

Cars at v/t in a radius may be a much easier and more definable lab demonstration of centripetal force.

Hoping this helps! Peter Hughes


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 (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 223
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: November 2011
Weclome To Newton

Argonne National Laboratory