- #1
williamcarter
- 153
- 4
Homework Statement
Homework Equations
0=viscous forces
0=in-out+sum of forces(0)
2*pi*r*L*τrz evaluated at r-2*pi*r*L*τrz evaluated at r+ΔR (eq1)
Dividing by volume and taking limit as δr->0 in eq1 I get :
(δτrz)/(δr) =0
My question is, how did they in solution got
(rδτrz)/(δr) =0, how do they have that additional r in the numerator?