The patch is a cylindrical disk 3mm thick with a radius of 1 cm. the drug is initially at a concentration of 50 mm. assume that the concentration in the adjacent skin is much less than the concentration in the patch.

Amixture of slurry and mud is to be pumped through a horizontal pipe of diameter 500 mm. the fluid behaves as a bingham plastic with a yield stress of 30 pa and viscosity 0.04 pa.s. describe the effects of the shear stress through a transverse section of the pipe by plotting the variation in shear stress and velocity profile: (i) just before the slurry starts to move (ii) as the slurry flows when the pressure gradient is double that in part (i)