3-22 Determine the pressure exerted an a diver at 30 m below the free surface of the sea. Assume a barometric pres- sure of 101 kPa and a specific pravity of 1.03 for seawater. Answer: 404.0 kPa

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105
CHAPTER 3
the pressure gage is 80 kPa, determine the distance between
the two fluid Jevels of the manometer if the fluid is (a) mer
cury (p = 13,600 kg/m') or th) water (p = 1000 kg/m')
numerical results with proper units, and take the density of
mercury to be 13,600 kg/m'.
3-22 Determine the pressure exerted on a diver at 30 m
below the free surface of the sea. Assume a barometric pres-
sure of 101 kPa and a specific pravity of 1.03 for seawater.
Answer: 404.0 Pa
3-27 O Reconsider Prob. 3-26. Using EES (or ocher)
software, investigate the effect of the manometer
fluid density in the range of 800 to 13,000 kg/m on the d
e dif-
ferential fluid height of the manometer. Plot the differential
fluid height against the density, and discuss the results.
3-23E Determine the pressure exerted on the surface af a
submarine cruising 300 ft below the free surface of the sea.
Assume that the harometric presure is 14.7 psia and the spe-
cific gravity of seawater is 103.
3-28 A manometer containing oil p = 850 kg/m') is
attached to a tank filled with air. If the oil-level difference
between the two columns is 45 cm and the atmaspheric pres
sure is 98 kPa, determine the absolute pressure of the air in
3-24 A gas is contained in a vertical, frictionless piston-
cylinder device. The piston has a mass of 4 kg and a cross-
sectional area of 35 em. A compressed spring above the pis-
ton exerts a force of 60 N on the piston. If the atmospheric
pressure is 95 kPa, determine the pressure inside the cylinder.
the tank. Answer: 101.75 kPa
3-29 A mercury manometer (p = 13,600 kgm') is con-
nected to an air duct to measure the pressure inside. The dif-
ference in the manometer levels is 15 mm, and the atmos-
pheric pressure is 100 kPa. (a) Judging from Fig. P3-29,
determine if the pressure in the duct is above or below the
atmospheric pressure. (b) Deter
the duct.
Answer 123,4 kPa
"ure in
979/ IPY
6ll N
P 95 kPa
Mp4 ke
AIR
M-35 cm
h 15 mm
P=1
FIGURE P3-24
3-25 E Reconsider Prob. 3-24. Using EES (or other)
saftware, investigate the effect of the spring
FIGURE P3-29
force in the range of 0 to 500 N on the pressure inside the
cylinder. Plot the pressure against the spring force, and dis-
cuss the results.
3-30 Repeat Prob. 3-29 for a differential mercury height of
30 mm.
3-26
Both a gage and a manometer are attached to a
gas tank to measure its pressure. If the reading on
3-31 Blood pressure is usually measured by wrapping a
closed air-filled jacket equipped with a pressure gage around
the upper arm of a person at the level of the heart. Using a
mercury manometer and a stethoscope, the systolic pressure
(the maximum pressure when the heart is pumping) and the
diastolic pressure (the minimum pressure when the heart is
resting) are measured in mmHg. The systolic and diastolic
pressures of a healthy person are about 120 mmHg and 80
mmHg, respectively, and are indicated as 120/80, Express
both of these gage pressures in kPa, psi, and meter water
column.
P-80 KPa
Gas
3-32 The maximum blood pressure in the upper arm of a
healthy person is about 120 mmHg. If a vertical tube open to
the atmosphere is connected to the vein in the arm of the per-
son, determine boIw high the blood will rise in the tube. Take
the density of the blood to be 1050 kg/m.
FIGURE P3-26
106
FLUID MECHANICS
manometer, as shown in Fig. P1-36. Determine the pressure
difference between the two pipelines. Take the density of sen-
water at that location to be p- 1035 kg/m'. Can the air col-
umn he ignored in the analysis?
3-37 Repeat Proh. 3-36 by replacing the air with oil whose
specific gravity is 0.72.
FO
3-38E The pressure in a natural gas pipeline is measured by
the manometer shown in Fig. P3-3SE with one of the arms
open to the atmosphere where the local atmospheric pressure
is 14.2 psia. Determine the absolute pressure in the pipeline.
Air
2 in
FIGURE P3-32
Nutual
Cias
10 in
3-33 Consider a 1.8-m-tall man standing vertically in water
and completely suhmerged in a poel. Determine the differ-
ence hetween the pressures acting at the head and at the toes
of this man, in kPa.
25 in
6 in
3-34 Consider a U-tube whose arms are open to the atmo-
sphere. Now water is poured into the U-tuhe from one arm,
and light vil (p - 790 kg/m') frem the other. One arm con-
tains 70-cm-high water, while the other arm contains both
fluids with an oil-to-water beight ratio of 6. Determine the
-Mercury
SG= 13.6
Water
height of each fluid in that amm.
FIGURE P3-3BE
3-39E Repeat Prob. 3-38E by replacing air by oil with a
specific gravity of 0.69.
3-40 The gage pressure of the air in the tank shown in Fig.
Oil
70 sm
P3 40 is measured to he 65 kPa Determine the differential
-Water
height k of the mercury column.
Cil
FIGURE P3-34
65 kPu
SG-072
75 cm
3-35 The hydraulic lift in a car repair shop has an output
diameter of 30 cm and is to lift cars up to 2000 kg. Deter-
mine the fluid gage pressure that must be maintained in the
Air
-Water
reservoir.
30 em
Mercury
SI- 116
3-36 Freshwater and seawater flowing in parallel borizontal
pipelines are connected to each other hy a double U-tuhe
Air
ー
FIGURE P3-40
Fresh-
water
40 cm
341 Repeat Prob. 3-40 for a gage pressure of 45 kPa.
Sea-
Transcribed Image Text:105 CHAPTER 3 the pressure gage is 80 kPa, determine the distance between the two fluid Jevels of the manometer if the fluid is (a) mer cury (p = 13,600 kg/m') or th) water (p = 1000 kg/m') numerical results with proper units, and take the density of mercury to be 13,600 kg/m'. 3-22 Determine the pressure exerted on a diver at 30 m below the free surface of the sea. Assume a barometric pres- sure of 101 kPa and a specific pravity of 1.03 for seawater. Answer: 404.0 Pa 3-27 O Reconsider Prob. 3-26. Using EES (or ocher) software, investigate the effect of the manometer fluid density in the range of 800 to 13,000 kg/m on the d e dif- ferential fluid height of the manometer. Plot the differential fluid height against the density, and discuss the results. 3-23E Determine the pressure exerted on the surface af a submarine cruising 300 ft below the free surface of the sea. Assume that the harometric presure is 14.7 psia and the spe- cific gravity of seawater is 103. 3-28 A manometer containing oil p = 850 kg/m') is attached to a tank filled with air. If the oil-level difference between the two columns is 45 cm and the atmaspheric pres sure is 98 kPa, determine the absolute pressure of the air in 3-24 A gas is contained in a vertical, frictionless piston- cylinder device. The piston has a mass of 4 kg and a cross- sectional area of 35 em. A compressed spring above the pis- ton exerts a force of 60 N on the piston. If the atmospheric pressure is 95 kPa, determine the pressure inside the cylinder. the tank. Answer: 101.75 kPa 3-29 A mercury manometer (p = 13,600 kgm') is con- nected to an air duct to measure the pressure inside. The dif- ference in the manometer levels is 15 mm, and the atmos- pheric pressure is 100 kPa. (a) Judging from Fig. P3-29, determine if the pressure in the duct is above or below the atmospheric pressure. (b) Deter the duct. Answer 123,4 kPa "ure in 979/ IPY 6ll N P 95 kPa Mp4 ke AIR M-35 cm h 15 mm P=1 FIGURE P3-24 3-25 E Reconsider Prob. 3-24. Using EES (or other) saftware, investigate the effect of the spring FIGURE P3-29 force in the range of 0 to 500 N on the pressure inside the cylinder. Plot the pressure against the spring force, and dis- cuss the results. 3-30 Repeat Prob. 3-29 for a differential mercury height of 30 mm. 3-26 Both a gage and a manometer are attached to a gas tank to measure its pressure. If the reading on 3-31 Blood pressure is usually measured by wrapping a closed air-filled jacket equipped with a pressure gage around the upper arm of a person at the level of the heart. Using a mercury manometer and a stethoscope, the systolic pressure (the maximum pressure when the heart is pumping) and the diastolic pressure (the minimum pressure when the heart is resting) are measured in mmHg. The systolic and diastolic pressures of a healthy person are about 120 mmHg and 80 mmHg, respectively, and are indicated as 120/80, Express both of these gage pressures in kPa, psi, and meter water column. P-80 KPa Gas 3-32 The maximum blood pressure in the upper arm of a healthy person is about 120 mmHg. If a vertical tube open to the atmosphere is connected to the vein in the arm of the per- son, determine boIw high the blood will rise in the tube. Take the density of the blood to be 1050 kg/m. FIGURE P3-26 106 FLUID MECHANICS manometer, as shown in Fig. P1-36. Determine the pressure difference between the two pipelines. Take the density of sen- water at that location to be p- 1035 kg/m'. Can the air col- umn he ignored in the analysis? 3-37 Repeat Proh. 3-36 by replacing the air with oil whose specific gravity is 0.72. FO 3-38E The pressure in a natural gas pipeline is measured by the manometer shown in Fig. P3-3SE with one of the arms open to the atmosphere where the local atmospheric pressure is 14.2 psia. Determine the absolute pressure in the pipeline. Air 2 in FIGURE P3-32 Nutual Cias 10 in 3-33 Consider a 1.8-m-tall man standing vertically in water and completely suhmerged in a poel. Determine the differ- ence hetween the pressures acting at the head and at the toes of this man, in kPa. 25 in 6 in 3-34 Consider a U-tube whose arms are open to the atmo- sphere. Now water is poured into the U-tuhe from one arm, and light vil (p - 790 kg/m') frem the other. One arm con- tains 70-cm-high water, while the other arm contains both fluids with an oil-to-water beight ratio of 6. Determine the -Mercury SG= 13.6 Water height of each fluid in that amm. FIGURE P3-3BE 3-39E Repeat Prob. 3-38E by replacing air by oil with a specific gravity of 0.69. 3-40 The gage pressure of the air in the tank shown in Fig. Oil 70 sm P3 40 is measured to he 65 kPa Determine the differential -Water height k of the mercury column. Cil FIGURE P3-34 65 kPu SG-072 75 cm 3-35 The hydraulic lift in a car repair shop has an output diameter of 30 cm and is to lift cars up to 2000 kg. Deter- mine the fluid gage pressure that must be maintained in the Air -Water reservoir. 30 em Mercury SI- 116 3-36 Freshwater and seawater flowing in parallel borizontal pipelines are connected to each other hy a double U-tuhe Air ー FIGURE P3-40 Fresh- water 40 cm 341 Repeat Prob. 3-40 for a gage pressure of 45 kPa. Sea-
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