GATE 2020 CE (CE2) – Question 59
A 600 mm diameter, 400 m long cast-iron pipe carries tank water to a free-air discharge 4.5 m below the tank surface. Darcy friction factor is 0.018 and g = 9.81 m/s². Find pipe velocity (m/s), to two decimals.
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Correct answer: 2.4 to 2.7
Explanation
Including outlet velocity head, Darcy friction $fL/D=12$ and the standard sharp-entry loss 0.5, Bernoulli gives $4.5=(1+0.5+12)V^2/(2g)$. Thus **2.56 m/s**. Entrance geometry is not specified; neglecting entry loss gives 2.61 m/s, also in the official 2.40–2.70 range.