Question

Consider the following statements related to Newtonian fluids:
A. Shear stress is proportional to shear rate
B. Viscosity remains constant at a given temperature
C. Milk behaves as a perfect Newtonian fluid
D. Apparent viscosity changes with shear rate indicates Newtonian fluid
E. Water is a Newtonian fluid
Choose the correct answer from the options given below:

• A. A, B, C only
• B. A, B, D only
• C. A, B, E only
• D. A, B, C, E only

Hint:

Newtonian = constant viscosity, linear relation.

Answer 1

The Correct Option is C

Concept: Newtonian fluids follow Newton’s law of viscosity where shear stress is directly proportional to shear rate, and viscosity remains constant.

Step 1: Evaluating Statement A.
\[ \tau = \mu \frac{du}{dy} \] Shear stress is proportional to shear rate → Correct.

Step 2: Evaluating Statement B.
For Newtonian fluids:
• Viscosity is constant at a given temperature Correct.

Step 3: Evaluating Statement C.
Milk:
• Slightly non-Newtonian due to fat globules Thus, not perfectly Newtonian → Incorrect.

Step 4: Evaluating Statement D.
Changing viscosity with shear rate:
• Indicates non-Newtonian behavior Hence, incorrect.

Step 5: Evaluating Statement E.
Water:
• Classic Newtonian fluid Correct.

Step 6: Final selection. \[ A, B, E \] Final Conclusion:
Option (3) is correct.