Correct Answer - Option 3 : Will be the same in both the pipes

**Concept:**

Friction factor (For laminar) \( = \frac{{64}}{{Re}}\)

As the Reynolds number is the same for both pipe flow.

**∴ The friction factor will be the same for both pipes.**

Relative roughness \( = \frac{K}{{\delta '}}\)

where k is the average height of the irregularities and δ’ is the thickness of laminar sub-layer

\(\frac{{\rm{k}}}{{{\rm{\delta '}}}} < 0.25 \Rightarrow {\rm{Smooth\;boundary}}\)

\(\frac{{\rm{k}}}{{{\rm{\delta '}}}} > 6 \Rightarrow {\rm{Rough\;boundary}}\)

\(0.25 < \frac{k}{{\delta '}} < 6.0 \Rightarrow Transition\;\)