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King Saud University
College of Engineering
Mechanical Engineering Department
ME 381: FLUID MECHANICS
First Semester First Examination (1428/1429 H)
time: 50 minutes
Question 1
(a) Define the following terms:
i. Fluid
ii. System
iii. Lagrangian method of description
iv. Eulerian method of description
Find the weight W needed to hold the
wall shown upright. Wall is 10 m wide.
Assume frictionless pivot. water = 999 kg/m3 & Patm = 101 kpa.
Question 2
(a) Find the absolute pressure PT in kpa at the top of the water pipe
shown. water = 999 kg/m3, SGmercury = 13.6 & Patm = 101 kpa.
(b)
(b) A wooden stick (SG = 0.5) is one meter long is floating with 13 cm
out of water. Determine the tension in the string. The stick’s crosssectional area is 2.0 cm2. water = 999 kg/m3.
Question 3
A velocity field is given by
V = 5 x (1 + t) i + 5 y (-1 + t) j
(a) Is the flow steady or unsteady?
(b) Is the flow 1-D, 2-D, 3-D, or uniform?
(c) Determine the u- and v-components of
the velocities.
(d) Determine the x(t) and y(t) if x = x0 and
y = y0 at t = 0.
Question 4
(a) Find the x and y components of the force required in N to hold the
bend shown in place. Pressures p1 and p2 are gage pressures.
(b) Indicate the dimensions and units of the following terms:
i. Pressure
ii. Shear stress
iii. Dynamic Viscosity
iv. Specific weight