7_Hydraulics Practice Quiz with Answer and Solution

Refresher - HYDRAULICS Quiz 7
PROBLEM 1:

A rectangular plate is vertically submerged half in oil having a specific gravity of
0.64 and half in water such that its top edge is flushed with the top surface of the
upper liquid and parallel to it. Obtain the ratio of the force exerted to the plate by
the water to that by the oil.

D

Solution:
h/2 0.84

P=γ hA
⎛ h⎞ ⎛ h⎞ h/2 1.0
Poil = 9.81(0.64) ⎜ ⎟ ⎜ ⎟ D
⎝ 4⎠ ⎝ 2⎠
Poil = 0.7848
⎛ h h⎞ ⎛ h⎞
Pwater = 9.81(1.0) ⎜ 0.64 • + ⎟ ⎜ ⎟ (D)
⎝ 2 4⎠ ⎝ 2⎠
Pwater = 2.7959
Pwater 2.7959 h2 D
=
Poil 0.7848 h2 D
Pwater
= 3.56
Poil

, Refresher - HYDRAULICS Quiz 7
PROBLEM 2-4:

Three pipes A, B and C are connected in parallel. If the combined discharged of the 3 pipes
is equal to 0.61 m3/s, and assuming they have equal values of friction factor "f", compute the
following using the tabulated data shown:
A
PIPELINE LENGTH DIAM.
A 600 m. 150 m.
B 480 m. 200 m. Q=0.61 B Q=0.61
C 750 m. 100 m.

➀ Compute the rate of flow of pipeline A in li/sec. C
➁ Compute the rate of flow of pipeline B in li/sec.
➂ Compute the rate of flow of pipeline C in li/sec.

Solution:
➀ Rate of flow of pipeline A:
hfA = hfB = hfC
0.0826 f LA QA2 0.0826 f LB QB2
(DA)5 = (DB)5
600 QA2 480 QB2
(0.15)5 = (0.2)5
QA = 0.436 QB ➁ Rate of flow of pipeline B:
QB = 2.295 QA QB = 2.295 QA
QB = 2.295(0.17)
600 QA2 750 QC2 QB = 0.39 m3/s
(0.15)5 = (0.10)5
QB = 390 liters/sec.
QA = 3.08 QC
QC = 0.325 QA ➂ Rate of flow of pipeline C:
QA + QB + QC = 0.61 QC = 0.325 QA
QA + 2.295 QA + 0.325 QA = 0.61 QC = 0.325 (0.17)
QA = 0.17 m3/s = 170 liters/sec. QC = 0.05 m3/s = 50 liters/sec.