FLUID-THBB

FLUID MECHANICS AND HYDRAULICS SITUATION I A pressure in a given tank reads 277 mm of mercury. Determine the equivalent height of column of water. a. 2.55 m c. 3.77 m b. 4.21 m d. 5.11 m

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Determine the equivalent height of column of kerosene with specific gravity of 0.82. a. 4.59 m c. 6.21 m b. 4.21 m d. 5.82 m

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Determine the equivalent height of column of nectar with specific gravity of 2.94. a. 1.87 m c. 2.31 m b. 1.96 m d. 1.28 m

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A block of wood floats in water with 20 cm projecting above the water surface. The same block when placed in oil (s = 0.80) floats with 15 cm projecting above the oil surface. Find the specific gravity of the block. a. 0.45 c. 0.50 b. 0.64 d. 0.72 SITUATION II An open cylindrical tank 1.2 m in diameter and 1.8 m deep is filled with water and rotated about its vertical axis at 60 revolutions per minute.

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How much water is spilled? a. 0.906 m3 c. 0.518 m3 b. 0.409 m3 d. 0.265 m3

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What is the minimum pressure at the bottom of the tank? a. 10.56 kPa c. 11.87 kPa b. 13.98 kPa d. 18.21 kPa

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A cubical tank is filled with 2 m of oil having specific gravity of 0.80. Find the force acting on the side of the tank when the acceleration is 5 m/s2 vertically downward. a. 14.89 kN c. 15.39 kN b. 20.54 kN d. 22.78 kN An open cylinder vessel 1 m in diameter contains water to a depth of 3.56 m. If it is rotated at a speed of 80 rpm about its vertical axis, determine the least depth of the vessel so that no water will be spilled out. a. 4.05 m c. 4.00 m b. 5.30 m d. 4.45 m A 4 – m diameter open cylindrical tank, 6 m high is filled with water. The tank is tilted to a position such that its water will occupy half of the area of the base. Determine the volume of water left in the tank. a. 13 m3 c. 14 m3 b. 16 m3 d. 15 m3 A dam rectangular in cross – section with upstream face vertical. Water is 20.4 m deep on the upstream side. The dam is 23.2 m high and 14.8 m wide at the base and weighs 2310 kg/m3. Coefficient of friction between the base and the foundation is 0.85. Compute the factor of safety against sliding. a. 3.85 c. 3.24 b. 2.67 d. 1.45 A dam 4 m on top, 18 m at the bottom and 24 m high has a water 20 m deep acting on its vertical side. What is the factor of safety against overturning? Assume weight of masonry to be 2400 kg/m3. a. 3.12 c. 1.87 b. 5.59 d. 3.29

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1.22 m 1.56 m

A block of wood 0.20 m thick is floating in seawater (s = 1.03). The specific gravity of the wood is 0.65. Find the minimum area of the wooden block to support a man weighing 80 kg. 2 2 a. 0.215 m c. 1.053 m b. 2.150 m2 d. 2.310 m2 An iceberg having a specific gravity of 0.92 is floating on salt water of specific gravity of 1.03. If the volume of ice above the water surface is 1000 3 m , what is the total volume of ice? 3 3 a. 9364 m c. 10422 m b. 8402 m3 d. 11789 m3 A tank with vertical sides, 3 m deep, 1.2 m square is filled to a depth of 2.7 m with water. A cube of wood (s = 0.50) measuring 60 cm on an edge is placed inside the container and floats. Find the weight of the volume of water displaced. a. 2.64 kN c. 5.48 kN b. 3.14 kN d. 1.06 kN SITUATION III The actual velocity in the contracted section of a jet of liquid flowing from a 2 inches diameter orifice is 28 ft/s under a head of 15 ft. Determine the value of the coefficient of velocity. a. 0.805 c. 0.409 b. 0.901 d. 0.706 If the measured discharge is 0.403 ft3/sec, determine the coefficient of contraction. a. 0.66 c. 0.56 b. 0.60 d. 0.54

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Determine the coefficient of discharge. a. O.485 c. 0.231 b. 0.387 d. 0.594

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A liquid having a specific gravity of 0.788 flows at 3.2 m/s through a 100 – mm diameter pipe line. Assume f = 0.0158. Find the head loss per kilometer of the pipe. a. 82.46 m c. 65.87 m b. 78.98 m d. 99.99 m

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A turbine is rated at 600 hp when the flow of water through it is 0.61 m3/s. Assuming efficiency of 87%, what is the head acting on the turbine? a. 98.76 m c. 76.95 m b. 85.97 m d. 100.23 m Neglecting air resistance, determine to what height a vertical jet of water could rise if projected with a velocity of 20 m/sec? a. 10.34 m c. 20.39 m b. 15.76 m d. 18.79 m SITUATION IV An orifice 80 mm in diameter was placed 0.96 m above the ground at the vertical side of an upright cylindrical tank 3 m in diameter. When opened, it hits the ground initially 2 m away from the orifice. The initial flow rate was 0.0161 m3/sec when water surface was 1.4 m above the orifice. How long will the jet reach the ground? a. 0.442 sec. c. 0.446 sec. b. 0.431 sec. d. 0.416 sec.

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Find the coefficient of velocity. a. 0.927 c. 0.735 b. 0.912 d. 0.863

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Determine the coefficient of discharge. a. 0.736 c. 0.612 b. 0.546 d. 0.805

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A rectangular channel 6.2 m by 1.2 m deep is lined with a smooth stone, well laid and has a hydraulic slope of 0.001. Use n = 0.013. What is the capacity of the channel? a. 14.32 m3/s c. 15.46 m3/s b. 16.43 m3/s d. 11.29 m3/s

c. 2.01 m d. 2.15 m

A wooden block having a specific gravity of 0.60, 40 mm x 60 mm x 3.5 m long is made to float in water. How many kilograms of stone having specific gravity of 3.25 should be attached at the bottom to make the wooden block float 300 mm exposed to atmosphere? a. 4.7 kg c. 3.8 kg b. 2.9 kg d. 3.2 kg

A stone weighs 460 N in air. When submerged in water, it weighs 300 N. Find the specific gravity of the stone. a. 3.214 c. 1.645 b. 2.141 d. 2.875

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From the figure as shown, find the value of “h”

a. b. 13.

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A body having a specific gravity of 0.70 floats on a liquid with specific gravity of 0.80. The volume of the body above the liquid surface is what percent of its total volume? a. 87.5% c. 12.5% b. 90% d. 10%

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What size of new cast iron pipe shall be used to carry 0.284 cubic meters per second with a head loss of 10.56 m per kilometer? n =0.019. a. 649 mm c. 498 mm b. 304 mm d. 513 mm

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1.8 m wide rectangular canal carries a flow of 2.4 3 m /s. What is the critical depth? a. 0.433 m c. 0.566 m b. 0.667 d. 0.812 m SITUATION V The hydraulic jump may be used as a crude flow meter. Suppose that in a horizontal rectangular channel 5 ft wide, the observed depths before and after a hydraulic jump are 0.66 ft and 3 ft respectively. 3 Find the flow rate in ft /sec. a. 43 c. 64 b. 54 d. 75 Find the head loss. a. 1.89 ft b. 1.23 ft

c. 1.62 ft d. 1.47 ft

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Determine the velocity after the jump. a. 2.9 ft/s c. 3.0 ft/s b. 4.3 ft/s d. 3.6 ft/s

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Water flows through a 2.5 cm diameter nozzle at the rate of 10 liters per second. Compute the dynamic force at the nozzle tip. a. 173 N c. 342 N b. 276 N d. 204 N

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A sharp crested 90O triangular weir carries water under a head of 1.2 m. Determine the discharge of the weir. a. 2.208 m3/sec c. 1.403 m3/sec b. 3.012 m3/sec d. 2.113 m3/sec

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Determine the force exerted by a 50 mm diameter jet moving 16 m/s against a perpendicular plate moving 8 m/s in the same direction as the jet. a. 289.9 N c. 251.3 N b. 567.8 N d. 754 N

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If water flows in uniformly at the rate of 45 ft3/s in a rectangular flume with width of 4 feet and a depth of 1.2 feet, what type of flow is it? a. Supercritical c. Subcritical b. Laminar d. Turbulent

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Water flows in a trapezoidal channel and running full. If the channel has a discharge of 8 m3/s, find the base width for a most efficient section. n =0.012, S = 0.0008. a. 2.02 m c. 1.64 m b. 2.59 m d. 1.77 m SITUATION VI Water is moving in a rectangular channel to have a Froude Number of 3.16. The channel is 5 m in width. The depth of flow is 1 m. If the water undergoes a hydraulic jump:

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Determine the depth of flow after the jump. a. 4m c. 3 m b. 5m d. 2 m

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Find the Froude number after the jump. a. 0.347 c. 0.395 b. 0.475 d. 0.565

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Compute the velocity after the jump a. 3.12 m/s c. 3.41 m/s b. 2.47 m/s d. 6.45 m/s

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A vertical jet of water thru a nozzle supports a load of 150 N. The velocity and diameter of the jet at the nozzle tip are 17.46 m/s and 3 cm respectively. Compute the distance of load from the nozzle tip. a. 6m c. 4 m b. 8m d. 10 m SITUATION VII Water is to flow in a rectangular flume at a rate of 1.42 m3/s at a slope of 0.0028. The width is equal to twice the depth. Use n = 0.017.

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Compute the normal depth of flow. a. 0.543 m c. 0.683 m b. 0.722 m d. 0.812 m

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Compute the Froude number. a. 0.224 c. 1.443 b. 1.322 d. 0.588

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Determine the type of flow. a. Laminar b. Critical c. Subcritical d. Supercritical

FLUID MECHANICS AND HYDRAULICS SITUATION VIII 3 Water flows at the rate of 25 m /s in a trapezoidal channel having a base width of 3 m and side slope of 4H:3V. The canal is lined with concrete (n = 0.013). 46.

Determine the critical depth. a. 1.523 m c. 1.768 m b. 1.155 m d. 1.667 m

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Compute the critical velocity. a. 2.432 m/s c. 4.655 m/s b. 5.212 m/s d. 3.263 m/s

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Critical slope is nearest to: a. 0.00445 b. 0.00193

c. 0.00172 d. 0.00512

SITUATION IX A hydraulic jump occurs in an efficient triangular 3 channel carrying 8 m /s on a slope of 0.006. The depth of water after the jump is 2.96 m. 49.

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Which of the following most nearly gives the depth before the jump? a. 0.952 m c. 0.723 m b. 0.843 m d. 0.732 m Determine the loss in energy in the jump a. 3.17 m c. 4.31 m b. 5.43 m d. 2.56 m

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Compute the loss of power in the jump. a. 339 kW c. 249 kW b. 427 kW d. 201 kW

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An old pipe is to be replaced by a new one with the same diameter and length. If the friction factor of the new is 2/3 of the old, compute the ratio of flow of the new to the old pipe. a. 0.85 c. 1.41 b. 1.22 d. 0.91 SITUATION X An open cylindrical tank 30 cm in diameter and 80 cm high partially filled with water is rotated about its vertical axis at a speed of 240 rpm.

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What would be the depth of water if the tank is brought to rest so that no water will be spilled out? a. 0.36 m c. 0.44 m b. 0.32 m d. 0.72 m

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At what speed would it be rotated so that 1.40 liters of water will be spilled out? a. 242.75 rpm c. 256.30 rpm b. 245.80 rpm d. 249.65 rpm

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At what speed should it be rotated so that the pressure at the center of the bottom of the tank is zero? a. 256.73 rpm c. 248.97 rpm b. 258.32 rpm d. 252.22 rpm

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A container 10 m wide and 10 m long contains water 2 m high and is accelerating to the right at a rate of 2.45 m/s2. Find the minimum pressure at the base. a. 5.65 kPa c. 8.45 kPa b. 7.37 kPa d. 9.14 kPa

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A 1.25 cm diameter orifice in a vertical wall of a tank under a constant head of 5.50 m discharges 0.45 m3 in 9.50 minutes. Find the coefficient of discharge. a. 0.48 c. 0.56 b. 0.62 d. 0.68 SITUATION XI A 3 m square plate is immersed vertically in water such that the two edges of the square are horizontal. The center of pressure is located 8 cm from the centroid of the square plate.

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Which of the following most nearly gives the distance of the top edge of the plate from the water surface? a. 6.38 m c. 7.88 m b. 9.38 m d. 10.88 m

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Which of the following most nearly gives the distance of the center of pressure from the water surface? a. 12.46 m c. 10.96 m b. 9.46 m d. 7.96 m

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Which of the following most nearly gives the total hydrostatic pressure on one side of the plate? a. 1092.59 kN c. 960.15 kN b. 827.72 kN d. 695.28 kN

SITUATION XII The following data shows the different sizes of pipes which a company wishes to use as a replacement for the old pipe system that they are using.

Cost of Pipe Annual Maintenance Cost Operating Cost/hour

100 mm ₱1,800,000

Diameter of Pipes 150 mm ₱1,120,000

250 mm ₱1,000,000

₱88,000

₱136,000

₱60,000

₱480

₱500

₱620

Total number of operating hours per year is 500. Replacement is done every 10 years at an interest of 10% per year. 61.

Which of the following gives the present worth of the 150 mm pipe? a. ₱3,491,803 c. ₱3,815,418 b. ₱3,273,490 d. ₱3,345,346

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Which of the following gives the equivalent annual cost of the 100 mm pipe. a. ₱650,578.4 c. ₱630,345.9 b. ₱620,941.7 d. ₱610,467.2

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Which of the following gives the most preferable pipe to be used as replacement? a. 250 mm c. 150 mm b. 100 mm d. 200 mm

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What are the most economical dimensions for a rectangular brick channel designed to carry 10 m3/s of water with a uniform flow? Use n = 0.015 and S = 0.001. a. b = 4.32 m, d = 2.15 m b. b = 3.28 m, d = 1.64 m c. b = 2.92 m, d = 1.47 m d. b = 3.86 m, d = 1.91 m

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Determine the bottom width of an earth canal having a sides slope of 2H:1V. If it is designed to have the most efficient trapezoidal section and to carry 6.0 m3/s with a grade of 40 cm/km. Assume n = 0.025 a. 0.58 m c. 0.67 m b. 0.85 m d. 1.35 m

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