What are thixotropic fluids characterized by?
Viscosity decreases GRADUALLY on stirring
Examples include yoghurt and gelatin.
What are rheopectic fluids characterized by?
Viscosity increases GRADUALLY on stirring
Rare examples include synovial fluid in joints.
What is the behavior of shear thinning (or pseudoplastic fluids)?
Viscosity decreases IMMEDIATELY as shear stress increases
Examples include nail varnish, paint, quicksand, and blood.
What is the behavior of shear thickening (or dilatant fluids)?
Viscosity increases IMMEDIATELY as shear stress increases
Examples include oobleck and damp sand that firms up when walked on.
What happens to the viscosity of fluids like custard and cornstarch when stress is applied?
They increase in viscosity
They behave like solids under stress.
What defines Newtonian fluids?
Viscosity remains constant at a given temperature or pressure
For example, if temperature stays the same, viscosity stays the same.
Define specific heat capacity.
The thermal energy required to raise the temperature of 1kg of a substance by 1˚C
It does not change.
Calculate the thermal energy required to raise the temperature of 4.6kg of golden syrup from 22˚C to 36˚C using C = 398 J/kg˚C.
E = 25631.2 J
Calculation: E = 4.6 x 398 x (36-22).
Calculate the specific heat capacity of treacle if 12kg is heated by 12˚C using E = 25631.2 J.
C = 178 J/kg˚C
Calculation: 25631.2 = 12 x c x 12.
What are Bingham plastics?
Materials that behave like solids at low stresses but flow at high stress
Examples include mayonnaise, butter, toothpaste, and ketchup.
