# Civil Engineering - UPSC Civil Service Exam Questions - Discussion

Discussion Forum : UPSC Civil Service Exam Questions - Section 27 (Q.No. 38)
38.
Two reservoirs at different surface elevations are connected by a set of two pipes A and B of same diameter and length in parallel. If the friction factor of A is 4 times that of the pipe B, what is the ratio of the discharge in A to that in B ?
0.25
4.0
2.0
0.5
Explanation:
No answer description is available. Let's discuss.
Discussion:
6 comments Page 1 of 1.

Rahul said:   1 year ago
Option D is correct.

H = flQ^2/12.1d^5.
Q1/Q2 = √ f2/f1.
= 1/2 or 0.5.

Apcivilian said:   2 years ago
Yes, the right answer is D.

Karthika.c said:   7 years ago
@Santu ans is 2 not 0.5.

f2/f1=1/2.
Q=A/V.
Q1/Q2=4 (v1/v2)^2.
Then elaborate Q1/Q2.

I.e (A1*v1)/(A2/v2)=4 (v1/V2)^then cancel v1/v2 on both sites.
We get,
Then A1/A2=4 [v1/v2].
Hence v1/v2=root of f2/f1 = 1/2.
So, the ans is A1/A2 = 4 * (1/2).
We get the ans 2. So answer c is correct.

Chhaya said:   7 years ago

Santu naskar said:   7 years ago