A Newtonian fluid is defined as the fluid which
- AIs incompressible and non-viscous
- BObeys Newton’s law of viscosityCorrect
- CIs highly viscous
- DIs compressible and non-viscous
Solution
Concept
Definition of Newtonian fluid
Formula
NONE
Step-by-step solution
1. Newtonian fluids exhibit a direct linear relationship between shear stress and shear strain rate. 2. By definition, a fluid that obeys Newton's law of viscosity (τ = μ × du/dy) is called a Newtonian fluid. 3. Examples include water, air, and gasoline under normal flow conditions. Answer: B
Explanation
A Newtonian fluid is characterized by a constant dynamic viscosity regardless of the applied shear rate. It strictly obeys Newton's law of viscosity, which states that shear stress is directly proportional to the rate of shear strain. Common examples include water, air, and gasoline, where viscosity does not change when stirred or pumped.
Why the other options are wrong
A) Incompressible and non-viscous fluids are classified as ideal fluids. C) High viscosity alone does not imply Newtonian behavior, which requires shear stress to be directly proportional to strain rate. D) Compressibility does not define Newtonian fluids, as Newtonian status depends solely on adherence to Newton's law of viscosity.
Shortcut
A Newtonian fluid directly obeys Newton's law of viscosity.
Common mistake
Confusing Newtonian fluids with ideal fluids, which are defined as incompressible and non-viscous.
Correct answer: B) Obeys Newton’s law of viscosity