physical analysis

Question 1

define viscosity

Answer 1

The resistance of a fluid to flow or change in shape. → shear stress/shear rate

Question 2

define shear stress

Answer 2

Shear stress in general is the intesnity of the force applied to deform. It is applied parallel to the surface. Example would be stiring milk into coffee, applying butter onto toast

Question 3

define normal stress

Answer 3

Is force applied perpendicular to a surface like when chewing a piece of gum

Question 4

define shear rate

Answer 4

the rate of change

Question 5

Define newtoninan vs non newtonian

Answer 5

Newtonian Fluid

• Viscosity stays constant and is independent of stress and time
• Flows predictably.
• Examples: Water, sugar solution, milk.

🔹 Non-Newtonian Fluid

• Viscosity changes depending on the applied force or time.
• Can become thicker or thinner under stress.
• Examples: Ketchup, yogurt, paint.

Question 6

What are the types of non-newtonian flows and define

Answer 6

1. Psuedoplastic flow: Viscosity decrases with increasing shear rate (independent of time), so flows more as force increases.
2. bingham plastic: Behave like solids until enough stress is applied, then behave like pesudoplastic fluids
3. thixotropic flow: Depend on time, viscosity will decrease over time while stiring but when left alone it thickens again often following gel→liquid→gel

Question 7

define alginates

Answer 7

weak gels at rest that become liquids under stress

Question 8

define yield stress

Answer 8

the minimum stress that must be applied for the dispersion to start flowing

Question 9

give examples of pseudoplastics (shear thinning), binghams plastic, and thixotropic flow fluids

Answer 9

1. linear polymers, yogurt, syrup,
2. ketchup
3. some sauces, aliginates