The distance from pipe boundary, at which the turbulent shear stress is one-third die wall shear stress, is (where R is the radius of pipe)
A
$$\frac{1}{3}{\text{R}}$$
B
$$\frac{1}{2}{\text{R}}$$
C
$$\frac{2}{3}{\text{R}}$$
D
$$\frac{3}{4}{\text{R}}$$
Correct Answer: $$\frac{1}{3}{\text{R}}$$