Some equations give the viscosity as an explicit function of shear stress, $=().$ Two equations of this

form are:

$=A+B[1+(\frac{}{C}{)}^2{]}^{-1}$

$=\frac{D}{1+u^m}$

where $A,B,C,D,E,$ and $m$ are constants.

a$.$ Which of the above models $($if either$)$ is capable of showing a zero$-$shear viscosity? What

is the zero$-$shear viscosity in terms of the constants.

b$.$ Repeat $($a$)$ for an infinite shear rate viscosity.

c$.$ Which $($if either$)$ can exhibit a power$-$law region? What is the power$-$law constant $n$ in

this region in terms of the parameters in the equation?