# Civil Engineering - UPSC Civil Service Exam Questions - Discussion

46.

At the same mean velocity, what is the ratio of head loss per unit length for a sewer pipe flowing full to that for the same pipe flowing half full ?

 [A]. 2 [B]. 1.7 [C]. 1 [D]. 0.6

Answer: Option A

Explanation:

No answer description available for this question.

 Sadashiva said: (Aug 23, 2018) Head loss due to friction/unit length of pipe is proportional to mean velocity square V^2 and inversely proportional to the diameter D of the pipe. V = volumetric flow rate remains same. So, the head loss due to friction: ratio when flowing full / when flowing half full = 1.

 Siddesh G M said: (Dec 12, 2018) Why not C?

 Jinish said: (Jan 21, 2020) Head loss = v^2/2g and v= q/a and a=3.14xd^2/4. So, for full flow D=d and half flow = d/2 now substitute value in head loss then ratio. So, it Will be 2.

 Aditya Kumar said: (Jul 24, 2020) Use the formula: Hf= flQ^2/12d^5. Since all other values will be same other than "d" For 1st condition - headloss =Q^2/d^5 = (A*V)^2/d^5. For 2nd condition- headloss = (A*v)^2/d^5, where d = d/2. divide 1 and 2. So, the answer is 2.

#### Post your comments here:

Name *:

Email   : (optional)

» Your comments will be displayed only after manual approval.

#### Current Affairs 2021

Interview Questions and Answers