# Q & A: Newtonian Fluids

Q:
What is a Newtonian Fluid?
- Ho Wai Yung (age 13)
Calgary,Alberta
A:
Ho Wai -

Whether or not a fluid is considered "Newtonian" depends on how the friction in the fluid depends on how rapidly the parts of it slide past each other. If you have two plates with a fluid between them and pull one past the other, the fluid makes a force between them. The force points toward making the two plates move at the same velocity. The amount of the force is proportional to a property of the fluid called its 'viscosity'. For Newtonian fluids the viscosity doesn't depend on how rapidly the plates are sliding past each other, and the net force is just proportional to their relative velocity. For non-Newtonian fluids the effective viscosity does depend on that relative velocity. Depending on the type of non-Newtonian fluid, the viscosity can either go up or down as the fluid is sheared more.

We have some other answers on non-Newtonian fluids. Try clicking on the "Category" link above, then "States of Matter and Energy", then  the sub-section called "".

Mike & Mats

(published on 10/22/2007)