Q.

Glycerine of density 1.25×103 kg m-3 is flowing through the conical section of a pipe. The area of cross-section of the pipe at its ends is 10 cm2 and 5 cm2 and the pressure drop across its length is 3 N m-2. The rate of flow of glycerine through the pipe is x×10-5 m3 s-1. The value of x is _________.              [2023]


Ans.

(4)

ΔP=P1-P2=3 N/m2  (given)

By continuity eqnA1v1=A2v2

 v1=A2A1v2                                       ...(i)

By Bernoulli's eqn,

P1+12ρv12=P2+12ρv22

P1-P2=12ρ(v22-v12)

ΔP=12ρ[1-(A2A1)2]v22

3=12×1.25×103[1-(510)2]v22

 v2=8×10-2 m/s

So discharge rate =A2v2=5×10-4×8×10-2=4×10-5 m3/s

Correct answer is x=4