Homework 1
Fluid Mechanics CE 3502 Spring, 2021
(upload your solution in PDF format)
For full credit, please show all of your calculations and clearly state any assumptions you made.
(1) A water bug of mass 10 g is suspended on the surface of a pond by surface tension (water does not wet the legs). The bug has six
legs. If each leg is in contact with the water over the same length L, what is that length
to keep it in equilibrium? What assumptions did you have to make to answer that
question?
(2) Calculate (a) the maximum capillary rise of water between two vertical glass plates
spaced 0.15 mm apart and (b) the minimum capillary drop if the same plates, now spaced
0.20 mm apart, are in mercury. Assume room temperature.
(3) A manometer is used to measure the pressure difference
between points A and B in a pipe as shown. Water flows in
the pipe, and the specific gravity of the manometer fluid is
S = 1.6. The distances and manometer deflection are
indicated on the figure. Find (a) the pressure differences pA pB in kPa and (b) the difference in piezometric head [ m]
between the same two points.
(4) For the gate shown below, α = 30°, z1 = 0.30 m, and z2 =
2.5 m. Will the gate fall or stay in position under the action
of the hydrostatic and gravity forces if the gate itself weighs
150 kN and is 1.0 m wide? Assume T = 10°C. Show your
calculations to justify your answer.
L=
L=?
9.5 cm
1.3 cm
Manometer
Fluid: S = 1.6
(5) The floating platform shown is supported at each of its four corners by a hollow sealed cylinder 1 m in diameter. Each cylinder
weighs 1.5 kN per meter of length. If the length of each cylinder L is as shown in the diagram below, and the platform floats
0.10 m above the water surface, what is the weight of the floating platform? Assume that the specific weight of the water (brackish)
is 10,000 N/m3. The platform is square in plan view.
Floating platform
Weight = ?
0.1
L = 3m