Correct Answer - Option 4 :

\(\frac{{3\pi}}{{10000}}\)
**Concept:**

For laminar flow, Maximum velocity occurs at centre.

∴ Umax = Centre–line velocity

For laminar flow, \({U_{avg}} = \frac{{{U_{max}}}}{2} \)

Discharge (Q) = Area × Average velocity

**Calculation:**

**Given:**

Pipe diameter, d = 0.04 m, Umax = Centre–line velocity = 1.5 m/s

\({U_{avg}} = \frac{{{U_{max}}}}{2} =\frac{{1.5}}{{2}}\Rightarrow 0.75\) m/s

Discharge (Q) = Area × Average velocity = \( \frac{\pi }{4} \times {\left( {0.04} \right)^2} \times 0.75 =\frac{{3\pi}}{{10000}}\) m^{3}/s.