Fluid Mechanics Question Viscous friction

Ste234

A flywheel of mass 45kg has a radius of gyration of 300mm.
When it is rotating at 600 rev/min, its speed reduces at 1 rev/min/s owing to fluid viscosity between the shaft and bearings, If the bearing length is 50mm, shaft diameter is 25mm and radial clearance is 0.05mm, determine the fluid viscosity.

I'm not really sure how to imagine this.
I'm not sure how to get started or what is really happening in this question.

ZRelation

This is a pretty classic fluid mechanics problem. There is a lubricating fluid in the annulus between the shaft and the surrounding bearings and you need to find its viscosity by accounting for the shaft power losses. The problem is solved in lots of the usual fluids texts but this one will get ya started.http://books.google.ie/books?id=nCnifcUdNp4C&pg=PA402&lpg=PA402&dq=fluid+mechanics+problem+rotating+shaft+bearing&source=bl&ots=3zBbNSKInb&sig=JQNuRy10NpHxeCc0UiubXTQfxhY&hl=en&ei=Eb6PTYmoJsWd4Qbl2dC_Cw&sa=X&oi=book_result&ct=result&resnum=2&ved=0CBsQ6AEwAQ#v=onepage&q&f=false