Answer :
According to the question, the radius of the vein is
r = 2 × 10-3 m
And the diameter of the vein is
d = 2 × 1 × 10-3 m = 2 × 10-3 m
The viscosity of blood is given by
η = 2.08 x 10-3 m
The density of blood is
ρ = 1.06 × 103 kg/m3
(a) It is known that NR = 2000, i.e., Reynolds’ number for laminar flow
Therefore, expression for the greatest average velocity of blood is
$ {{V}_{avg}}=\frac{{{N}_{R}}\eta }{\rho d}=\frac{2000\times 2.084\times {{10}^{-3}}}{1.06\times {{10}^{3}}\times 4\times {{10}^{-3}}} $
$ {{V}_{avg}}=0.983m/s $
(b) The flow rate is given by
R = Vavg π r2
R = 0.983 x 3.14 x ( 10-3)2
R = 1.235 x 10-6 m3/s