Influence of viscosity force force <- Frictional force <-- Frictional force Tuggin force Tangential force per unit area ---Shear stress t t=OV(n)onTuggin force → Influence of viscosity Tangential force per unit area ---Shear stress t t = V(n)/n <--- Frictional force <--- Frictional force <--- Frictional force <--- Frictional force