Solved: An office worker claims that a cup of cold coffee

Problem 124P At sea level, the weight of 1 kg mass in SI units is 9.81 N. The weight of 1 lbm mass in English units is (a) 1 lbf ________________ (b) 9.81 lbf ________________ (c) 32.2 lbf ________________ (d) 0.1 lbf ________________ (e) 0.031 lbf

Why does a bicyclist pick up speed on a downhill road even when he is not pedaling? Does this violate the conservation of energy principle?

Problem 3P One of the most amusing things a person can experience is when a car in neutral appears to go uphill when its Brakes are released. Can this really happen or is it an optical illusion? How can you verify if a road is pitched uphill or downhill?

Problem 1P What is the difference between the classical and the statistical approaches to thermodynamics?

Problem 4P An office worker claims that a cup of cold coffee on his table warmed up to 80°C by picking up energy from the surrounding air, which is at 25°C. Is there any truth to bis claim? Does this process violate any thermodynamic laws?

Problem 5P What is the difference between kg-mass and kg force?

Problem 6P Explain why the light-year has the dimension of length.

Problem 7P What is the net force acting on a car cruising at a constant velocity of 70 km/h (a) on a level road and (b) on an uphill road?

At \(45^{\circ}\) latitude, the gravitational acceleration as a function of elevation \(z\) vabove sea level is given by \(g=a-b z\), where \(a=9.807 \mathrm{~m} / \mathrm{s}^{2}\) and \(b=3.32 \times 10^{-6} \mathrm{~s}^{-2}\). Determine the height above sea level where the weight of an object will decrease by \(0.3\) percent. Equation Transcription: 45° Text Transcription: 45 degree g=a-bz a=9.807 m/s^2 b=3.32 times 10-6 s^-2

Problem 9P What is the weight, in N, of an object with a mass of 200 kg at a location where g = 9.6 m/s2?

Problem 11P The constant-pressure specific heat of air at 25°C is 1.005 kJ/kg·°C. Express this value in kJ/kg·K, J/g·°C, kcal/kg·°C, and Btu/lbm·°F.

A \(3-\mathrm{kg}\) rock is thrown upward with a force of \(200 \mathrm{~N}\) at a location where the local gravitational acceleration is \(9.79 \mathrm{~m} / \mathrm{s}^{2}\). Determine the acceleration of the rock, in \(\mathrm{m} / \mathrm{s}^{2}\). Equation Transcription: Text Transcription: 3-kg 200 N 9.79 m/s^2 m/s^2

Solve Prob. 1–12 using \(\mathrm{EES}\) (or other) software. Print out the entire solution, including the numerical results with proper units. Equation Transcription: Text Transcription: EES

A 3-kg plastic tank that has a volume of \(0.2 \mathrm{~m}^{3}\) is filled with liquid water. Assuming the density of water is \(1000 \mathrm{~kg} / \mathrm{m}^{3}\), determine the weight of the combined system. Equation Transcription: Text Transcription: 3-kg 0.2 m^3 1000 kg/m^3

Problem 14P A 4-kW resistance heater in a water heater runs for 3 hours to raise the water temperature to the desired level. Determine the amount of electric energy used in both kWh and kJ.

The gas tank of a car is filled with a nozzle that discharges gasoline at a constant flow rate. Based on unit considerations of quantities, obtain a relation for the filling time in terms of the volume \(V\) of the tank (in \(L\)) and the discharge rate of gasoline \(V(in\ L/s)\). Equation Transcription: Text Transcription: V(in L/s) V L

Problem 17P A pool of volume V (in m3) is to be filled with water using a hose of diameter D(in m). If the average discharge velocity is V (in m/s) and the filling time is t (in s), obtain a relation for the volume of the pool based on until considerations of quantities involved.

A \(150-lbm\) astronaut took his bathroom scale (a spring scale and a beam scale (compares masses) to the moon where the local gravity is \(g=5.48 \mathrm{ft} / \mathrm{s}^{2}\). Determine how much he will weigh (a) on the spring scale and (b) on the beam scale. Equation Transcription: Text Transcription: 150-lbm g = 5.48 ft/s^2

A large fraction of the thermal energy generated in the engine of a car is rejected to the air by the radiator through the circulating water. Should the radiator be analyzed as a closed system or as an open system? Explain.

Problem 20P A can of soft drink at room temperature is put into the refrigerator so that it will cool. Would you model the can of soft drink as a closed system or as an open system? Explain.

Problem 19P You are trying to understand how a reciprocating air compressor (a piston-cylinder device) works. What system would you use? What type of system is this?

Problem 21P What is the difference between intensive and extensive properties?

Problem 22P Is the weight of a system an extensive or intensive property?

Problem 23P Is the state of the air in an isolated room completely specified by the temperature and the pressure? Explain.

The molar specific volume of a system \(\bar{v}\) is defined as the ratio of the volume of the system to the number of moles of substance contained in the system. Is this an extensive or intensive property? Equation Transcription: Text Transcription: bar v

Problem 25P What is a quasi-equilibrium process? What is its importance in engineering?

Problem 26P Define the isothermal, isobaric, and isochoric processes.

Problem 27P How would you describe the state of the water in a bathtub? How would you describe the process that this water experiences as it cools?

Problem 28P When analyzing the acceleration of gases as they flow through a nozzle, what would you choose as your system? What type of system is this?

Problem 29P What is specific gravity? How is it related to density?

The density of atmospheric air varies with elevation, decreasing with increasing altitude, (a) Using the data given in the table, obtain a relation for the variation of density with elevation, and calculate the density at an elevation of \(7000\ m\). (b) Calculate the mass of the atmosphere using the correlation you obtained. Assume the earth to be a perfect sphere with a radius of \(6377\ km\), and take the thickness of the atmosphere to be \(25\ km\). Equation Transcription: Text Transcription: 7000 m 6377 km 25 km

Problem 31P What are the ordinary and absolute temperature scales in the SI and the English system?

Problem 32P Consider an alcohol and a mercury thermometer that read exactly 0°C at the ice point and 100°C at the steam point. The distance between the two points is divided into 100 equal parts in both thermometers. Do you think these thermometers will give exactly the same reading at a temperature of, say, 60°C? Explain.

Problem 34P The deep body temperature of a healthy person is 37°C. What is it in kelvins?

Problem 35P What is the temperature of the heated air at 150°C in °F and R?

Problem 36P The temperature of a system rises by 70°C during a heating process. Express this rise in temperature in kelvins.

Problem 37P The flash point of an engine oil is 363°F. What is the absolute flash-point temperature in K and R?

Problem 33P Consider two closed systems A and B. System A contains 3000 kJ of thermal energy at 20°C, whereas system B contains 200 kJ of thermal energy at 50°C. Now the systems are brought into contact with each other. Determine the direction of any heat transfer between the two systems.

Problem 38P The temperature of ambient air in a certain location is measured to be ?40°C. Express this temperature in Fahrenheit (°F), Kelvin (K), and Rankine (R) units.

Problem 40P Explain why some people experience nose bleeding and some others experience shortness of breath at high elevations.

Problem 41P A health magazine reported that physicians measured 100 adults’ blood pressure using two different arm positions: parallel to the body (along the side) and perpendicular to the body (straight out). Readings in the parallel position were up to 10 percent higher than those in the perpendicular position, regardless of whether the patient was standing, sitting, or lying down. Explain the possible cause for the difference.

Problem 39P The temperature of a system drops by 45°F during a cooling process. Express this drop in temperature in K, R, and °C.

Problem 42P Someone claims that the absolute pressure in a liquid of constant density doubles when the depth is doubled. Do you agree? Explain.

Problem 43P Express Pascal’s law, and give a real-world example of it.

Problem 45P A vacuum gage connected to a chamber reads 35 kPa at a location where the atmospheric pressure is 92 kPa. Determine the absolute pressure in the chamber.

Problem 46P The pressure in a compressed air storage tank is 1200 kPa. What is the tank’s pressure in (a) kN and m units; (b) kg, m, and s units; and (c) kg, km, and s units?

Problem 44P Consider two identical fans, one at sea level and the other on top of a high mountain, running at identical speeds. How would you compare (a) the volume flow rates and (b) the mass flow rates of these two fans?

Problem 48P If the pressure inside a rubber balloon is 1500 mmHg, what is this pressure in pounds-force per square inch (psi)?

Problem 47P The pressure in a water line is 1500 kPa. What is the line pressure in (a) lb/ft2 units and (b) lbf/in2 (psi) units?

The water in a tank is pressurized by air, and the pressure is measured by a multifluid manometer as shown in Fig. Pl-50. Determine the gage pressure of air in the tank if \(h_{1}=0.2 \mathrm{~m}, h_{2}=0.3 \mathrm{~m}\), and \(h_{3}=0.4 \mathrm{~m}\). Take the densities of water, oil, and mercury to be \(1000 \mathrm{~kg} / \mathrm{m}^{3}, 850 \mathrm{~kg} / \mathrm{m}^{3}\), and \(13,600 \mathrm{~kg} / \mathrm{m}^{3}\), respectively. Equation Transcription: Text Transcription: h_1=0.2 m,h_2=0.3 m h_3=0.4 m 1000 kg/m^3,850 kg/m^3 13,600 kg/m^3

Problem 49P A manometer is used to measure the air pressure in a tank. The fluid used has a specific gravity of 1.25, and the differential height between the two arms of the manometer is 28 in. If the local atmospheric pressure is 12.7 psia, determine the absolute pressure in the tank for the cases of the manometer arm with the (a) higher and (b) lower fluid level being attached to the tank.

Problem 51P Determine the atmospheric pressure at a location where the barometric reading is 750 mm Hg. Take the density of mercury to be 13,600 kg/m3.

Problem 53P The gage pressure in a liquid at a depth of 3 m is read to be 42 kPa. Determine the gage pressure in the same liquid at a depth of 9 m.

Problem 55P Determine the pressure exerted on the surface of a submarine cruising 175 ft below the free surface of the sea. Assume that the barometric pressure is 14.7 psia and the specific gravity of seawater is 1.03.

Problem 54P The absolute pressure in water at a depth of 9 m is read to be 185 kPa. Determine (a) the local atmospheric pressure, and (b) the absolute pressure at a depth of 5 m in a liquid whose specific gravity is 0.85 at the same location.

A 200-pound man has a total foot imprint area of \(72 \mathrm{in}^{2}\). Determine the pressure this man exerts on the ground if \((a)\) he stands on both feet and \((b)\) he stands on one foot. Equation Transcription: Text Transcription: 200-pound 72 in^2

Problem 57P The vacuum pressure of a condenser is given to be 80 kPa. If the atmospheric pressure is 98 kPa, what is the gage pressure and absolute pressure in kPa, kN/m2, lbf/in2, psi, and mm Hg.

Problem 56P Consider a 70-kg woman who has a total foot imprint area of 400 cm2. She wishes to walk on the snow, but the snow cannot withstand pressures greater than 0.5 kPa. Determine the minimum size of the snowshoes needed (imprint area per shoe) to enable her to walk on the snow without sinking.

Problem 58P The barometer of a mountain hiker reads 750 mbars at the beginning of a hiking trip and 650 mbars at the end. Neglecting the effect of altitude on local gravitational acceleration, determine the vertical distance climbed. Assume an average air density of 1.20 kg/m3.

Solve Prob. 1–59 using \(\mathrm{EES}\) (or other) software. Print out the entire solution, including the numerical results with proper units. Equation Transcription: Text Transcription: EES

A gas is contained in a vertical, frictionless pistoncylinder device. The piston has a mass of \(3.2 \mathrm{~kg}\) and a crosssectional area of \(35 \mathrm{~cm}^{2}\). A compressed spring above the piston exerts a force of \(150 \mathrm{~N}\) on the piston. If the atmospheric pressure is \(95 \mathrm{kPa}\), determine the pressure inside the cylinder. Equation Transcription: Text Transcription: 3.2 kg 35 cm^2 150 N

The basic barometer can be used to measure the height of a building. If the barometric readings at the top and at the bottom of a building are 675 and \(695 \mathrm{mmHg}\), respectively, determine the height of the building. Take the densities of air and mercury to be \(1.18 \mathrm{~kg} / \mathrm{m}^{3}\) and \(13,600 \mathrm{~kg} / \mathrm{m}^{3}\), respectively. Equation Transcription: Text Transcription: 695 mmHg 1.18 kg/m^3 13,600 kg/m^3

Problem 61P The hydraulic lift in a car repair shop has an output diameter of 30 cm and is to lift cars up to 2000 kg. Determine the fluid gage pressure that must be maintained in the reservoir.

Both a gage and a manometer are attached to a gas tank to measure its pressure. If the reading on the pressure gage is \(80 \mathrm{kPa}\), determine the distance between the two fluid levels of the manometer if the fluid is \((a)\) mercury \(\left(\rho=13,600 \mathrm{~kg} / \mathrm{m}^{3}\right)\) or \((b)\) water \(\left(\rho=1000 \mathrm{~kg} / \mathrm{m}^{3}\right)\). Equation Transcription: Text Transcription: 80 kPa rho= 13,600 kg/m^3 rho=1000 kg/m^3

Reconsider Prob. 1–62. Using \(\mathrm{EES}\) (or other) software, investigate the effect of the spring force in the range of 0 to \(500 \mathrm{~N}\) on the pressure inside the cylinder. Plot the pressure against the spring force, and discuss the results. Equation Transcription: Text Transcription: EES 500 N

Reconsider Prob. 1–64. Using \(\mathrm{EES}\) (or other) software, investigate the effect of the manometer fluid density in the range of 800 to \(13,000 \mathrm{~kg} / \mathrm{m}^{3}\)on the differential fluid height of the manometer. Plot the differential fluid height against the density, and discuss the results. Equation Transcription: Text Transcription: EES 13,000 kg/m^3

Problem 66P A manometer containing oil (p = 850 kg/m3) is attached to a tank filled with air. If the oil-level difference between the two columns is 80 cm and the atmospheric pressure is 98 kPa, determine the absolute pressure of the air in the tank.

Problem 68P Repeat Prob. 1–72 for a differential mercury height of 45 mm.

The pressure in a natural gas pipeline is measured by the manometer shown in Fig. P1–69E with one of the arms open to the atmosphere where the local atmospheric pressure is \(14.2 \mathrm{psia}\). Determine the absolute pressure in the pipeline. Equation Transcription: Text Transcription: 14.2 psia

A mercury manometer \(\left(\rho=13,600 \mathrm{~kg} / \mathrm{m}^{3}\right)\) is connected to an air duct to measure the pressure inside. The difference in the manometer levels is \(15 \mathrm{mm}\), and the atmospheric pressure is \(100 \mathrm{kPa}\). (a) Judging from Fig. P1?72, determine if the pressure in the duct is above or below the atmospheric pressure. (b) Determine the absolute pressure in the duct. Equation Transcription: Text Transcription: rho= 13,600 kg/m^3 15 mm 100 kPa

Repeat Prob. 1–69E by replacing air by oil with a specific gravity of \(0.69\). Equation Transcription: Text Transcription: 0.69

The maximum blood pressure in the upper arm of a healthy person is about \(120 \mathrm{mmHg}\). If a vertical tube open to the atmosphere is connected to the vein in the arm of the person, determine how high the blood will rise in the tube. Take the density of the blood to be \(1050 \mathrm{~kg} / \mathrm{m}^{3}\). Equation Transcription: Text Transcription: 120 mmHg 050 kg/m^3

Problem 71P 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 mm Hg. The systolic and diastolic pressures of a healthy person are about 120 mm Hg and 80 mm Hg, respectively, and are indicated as 120/80. Express both of these gage pressures in kPa, psi, and meter water column.

Problem 73P Determine the pressure exerted on a diver at 45 m below the free surface of the sea. Assume a barometric pressure of 101 kPa and a specific gravity of 1.03 for seawater.

Consider a U-tube whose arms are open to the atmosphere. Now water is poured into the U-tube from one arm, and light oil \(\left(\rho=790 \mathrm{~kg} / \mathrm{m}^{3}\right)\) from the other. One arm contains \(70 -cm-high\) water, while the other arm contains both fluids with an oil-to-water height ratio of 4 . Determine the height of each fluid in that anm. Equation Transcription: Text Transcription: rho= 790 kg/m^3

Consider a double-fluid manometer attached to an air pipe shown in Fig. P1–75. If the specific gravity of one fluid is \(13.55\), determine the specific gravity of the other fluid for the indicated absolute pressure of air. Take the atmospheric pressure to be \(100 \mathrm{kPa}\). Equation Transcription: Text Transcription: 13.55 100 kPa

Problem 79E Consider the manometer in Fig. P1?80. If the specific weight of fluid A is 100 kN/m3, what is the absolute pressure, in kPa, indicated by the manometer when the local atmospheric pressure is 90 kPa?

Freshwater and seawater flowing in parallel horizontal pipelines are connected to each other by a double U-tube manometer, as shown in Fig. P1?76. Determine the pressure difference between the two pipelines. Take the density of seawater at that location to be \(\rho=1035 \mathrm{~kg} / \mathrm{m}^{3}\). Can the air column be ignored in the analysis? Equation Transcription: Text Transcription: rho= 1035 kg/m^3

Problem 77P Repeat Prob. 1–78 by replacing the air with oil whose specific gravity is 0.72.

Consider the manometer in Fig. P1-78. If the specific weight of fluid \(B\) is \(20 \mathrm{kN} / \mathrm{m}^{3}\), what is the absolute pressure, in \(\mathrm{kPa}\), indicated by the manometer when the local atmospheric pressure is \(720 \mathrm{mmHg}\) ? Equation Transcription: Text Transcription: B 20 kN/m^3 kPa 720 mmHg

Consider the system shown in Fig. P1-81. If a change of \(0.7 \mathrm{kPa}\) in the pressure of air causes the brine-mercury interface in the right column to drop by \(5 \mathrm{~mm}\) in the brine level in the right column while the pressure in the brine pipe remains constant, determine the ratio of \(A_{2} / A_{1}\) Equation Transcription: Text Transcription: 0.7 kPa 5 mm A_2/A_1

Determine a positive real root of this equation using EES: \(2 x^{3}-10 x^{0.5}-3 x=-3\) Equation Transcription: Text Transcription: EES 2x^3-10x^0.5 -3x =-3

Solve this system of three equations with three unknowns using EES: \(x^{2} y-z=1\) \(x-3 y^{05}+x z=-2\) \(x+y-z=2\) Equation Transcription: Text Transcription: x^2 y-z = 1 x - 3y^0.5 + xz = -2 x + y - z = 2

Problem 82P What is the value of the engineering software packages in (a) engineering education and (b) engineering practice?

Calculate the absolute pressure, \(P_{1}\), of the manometer shown in Fig. P1-78 in kPa. The local atmospheric pressure is \(758 \mathrm{mmHg}\). Equation Transcription: Text Transcription: P_1 kPa 758 mmHg

Solve this system of two equations with two unknowns using EES: \(x^{3}-y^{2}=7.75\) \(3 x y+y=3.5\) Equation Transcription: Text Transcription: x^3-y^2=7.75 3xy + y = 3.5

Solve this system of three equations with three unknowns using EES: \(2 x-y+z=7\) \(3 x^{2}+3 y=z+3\) \(x y+2 z=4\) Equation Transcription: Text Transcription: 2x - y + z = 7 3x^2+ 3y = z + 3 xy + 2z = 4

Specific heat is defined as the amount of energy needed to increase the temperature of a unit mass of a substance by one degree. The specific heat of water at room temperature is \(4.18 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\) in SI unit system. Using the unit conversion function capability of EES, express the specific heat of water in \((a) \mathrm{kJ} / \mathrm{kg} \cdot \mathrm{K},(b) \mathrm{B} \mathrm{tw} / \mathrm{lbm} \cdot{ }^{\circ} \mathrm{F}\), (c) Btu/lbm-R, and \((d) \mathrm{kcal} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\) units. Equation Transcription: °C °F °C Text Transcription: 4.18 kJ/kg dot degree celsius kJ/kg dot K Btu/lbm dot degree fahrenheit kcal/kg dot degree celsius

A hydraulic lift is to be used to lift a \(2500\ kg\) weight by putting a weight of \(25\ kg\) on a piston with a diameter of \(10\ cm\). Determine the diameter of the piston on which the weight is to be placed. FIGURE P1–91 Equation Transcription: Text Transcription: 2500 kg 25 kg 10 cm

Problem 88P The weight of bodies may change somewhat from one location to another as a result of the variation of the gravitational acceleration g with elevation. Accounting for this variation using the relation in Prob. 1–8, determine the weight of an 80-kg person at sea level (z = 0), in Denver (z = 1610 m), and on the top of Mount Everest (z = 8848 m).

Problem 89P A man goes to a traditional market to buy a steak for dinner. He finds a 12-oz steak (1 lbm = 16 oz) for $5.50. He then goes to the adjacent international market and finds a 300-g steak of identical quality for $5.20. Which steak is the better buy?

Problem 90P What is the weight of a 1-kg substance in N, kN, kg·m/s2, kgf, lbm-ft/s2, and lbf?

Problem 93P Hyperthermia of 5°C (i.e., 5°C rise above the normal body temperature) is considered fatal. Express this fatal level of hyperthermia in (a) K, (b) °F, and (c) R.

Problem 92P The efficiency of a refrigerator increases by 3 percent for each °C rise in the minimum temperature in the device. What is the increase in the efficiency for each (a) K, (b) °F, and (c) R rise in temperature?

Problem 94P A house is losing heat at a rate of 1800 kJ/h per °C temperature difference between the indoor and the outdoor temperatures. Express the rate of heat loss from this house per (a) K, (b) °F, and (c) R difference between the indoor and the outdoor temperature.

The average temperature of the atmosphere in the world is approximated as a function of altitude by the relation \(T_{\mathrm{atm}}=288.15-6.5 \mathrm{z}\) where \(T_{\text {atm }}\) is the temperature of the atmosphere in \(\mathrm{K}\) and \(z\) is the altitude in \(\mathrm{km}\) with \(z=0\) at sea level. Determine the average temperature of the atmosphere outside an airplane that is cruising at an altitude of \(12,000 \mathrm{~m}\). Equation Transcription: Text Transcription: T_atm= 288.15 - 2 6.5z T_atm K z z=0 12,000 m

Problem 96P Joe Smith, an old-fashioned engineering student, believes that the boiling point of water is best suited for use as the reference point on temperature scales. Unhappy that the boiling point corresponds to some odd number in the current absolute temperature scales, he has proposed a new absolute temperature scale that he calls the Smith scale. The temperature unit on this scale is smith, denoted by S, and the boiling point of water on this scale is assigned to be 1000 S. From á thermodynamic point of view, discuss if it is an acceptable temperature scale. Also, determine the ice point of water on the Smith scale and obtain a relation between the Smith and Celsius scales.

It is well-known that cold air feels much colder in windy weather than what the thermometer reading indicates because of the "chilling effect" of the wind. This effect is due to the increase in the convection heat transfer coefficient with increasing air velocities. The equivalent wind chill temperature in \({ }^{\circ} \mathrm{F}\) is given by [ASHRAE, Handbook of Fundamentals (Atlanta, GA, 1993), p. 8.15] \(T_{\text {equiv }}=& 91.4-\left(91.4-T_{\text {ambient }}\right) \times(0.475-0.0203 V+0.304 \sqrt{V})\) where \(V\) is the wind velocity in \(\mathrm{mi} / \mathrm{h}\) and \(T_{\text {ambient }}\) is the ambient air temperature in \({ }^{\circ} \mathrm{F}\) in calm air, which is taken to be air with light winds at speeds up to \(4 \mathrm{mi} / \mathrm{h}\). The constant \(91.4^{\circ} \mathrm{F}\) in the given equation is the mean skin temperature of a resting person in a comfortable environment. Windy air at temperature \(T_{\text {ambient }}\) and velocity \(V\) will feel as cold as the cal?n air at temperature \(T_{\text {equiv }}\). Using proper conversion factors, obtain an equivalent relation in SI units where \(V\) is the wind velocity in \(\mathrm{km} / \mathrm{h}\) and \(T_{\text {ambient }}\) is the ambient air temperature in \9{ }^{\circ} \mathrm{C}\). Equation Transcription: Text Transcription: degree Fahrenheit T_equiv = 91.4-(91.4-T_ambient) times (0.475-0.0203V+0.304 square root V) V mi/h T_ambient 4mi/h 91.4 degree Fahrenheit T_equiv degree Celsius

Reconsider Prob. 1-97E. Using EES (or other) software, plot the equivalent wind chill temperatures in \({ }^{\circ} \mathrm{F}\) as a function of wind velocity in the range of 4 to \(40 \mathrm{mph}\) for the ambient temperatures of 20,40 , and \(60^{\circ} \mathrm{F}\). Discuss the results. Equation Transcription: Text Transcription: EES degree Fahrenheit 40 mph 60 degree Fahrenheit

Problem 101P The average body temperature of a person rises by about 2°C during strenuous exercise. What is the rise in the body temperature in (a) K, (b) °F, and (c) R during strenuous exercise?

A vertical piston-cylinder device contains a gas at a pressure of \(100 \mathrm{kPa}\). The piston has a mass of \(5 \mathrm{~kg}\) and a diameter of \(12 \mathrm{~cm}\). Pressure of the gas is to be increased by placing some weights on the piston. Determine the local atmospheric pressure and the mass of the weights that will double the pressure of the gas inside the cylinder. FIGURE P1-99 Equation Transcription: Text Transcription: 100kPa 5 kg 12 cm

Balloons are often filled with helium gas because it weighs only about one-seventh of what air weighs under identical conditions. The buoyancy force, which can be expressed as \(F_{b}=\rho_{\text {air }} g V_{\text {balloon }}\), will push the balloon upward. If the balloon has a diameter of \(12 \mathrm{~m}\) and carries two people, \(85 \mathrm{~kg}\) each, determine the acceleration of the balloon when it is first released. Assume the density of air is \(\rho=1.16 \mathrm{~kg} / \mathrm{m}^{3}\), and neglect the weight of the ropes and the cage. FIGURE P1–102 Equation Transcription: Text Transcription: F_b=rho_air gV_balloon 12 m 85 kg rho=1.16 kg/m^3

An air-conditioning system requires a 35-m-long section of \915-\mathrm{cm}\) diameter duct work to be laid underwater. Determine the upward force the water will exert on the duct. Take the densities of air and water to be \(1.3 \mathrm{~kg} / \mathrm{m}^{3}\) and \(1000 \mathrm{~kg} / \mathrm{m}^{3}\), respectively. Equation Transcription: Text Transcription: 35-m 15-cm 1.3 kg/m^3 1000 kg/m^3

Reconsider Prob. 1–102. Using \(\mathrm{EES}\) (or other) software, investigate the effect of the number of people carried in the balloon on acceleration. Plot the acceleration against the number of people, and discuss the results. Equation Transcription: Text Transcription: EES

Problem 104P Detennine the maximum amount of load, in kg, the balloon described in Prob. 1–109 can carry.

The lower half of a \(6-\mathrm{m}\)-high cylindrical container is filled with water \(\left(\rho=1000 \mathrm{~kg} / \mathrm{m}^{3}\right)\) and the upper half with oil that has a specific gravity of \(0.85\). Determine the pressure difference between the top and bottom of the cylinder. FIGURE P1–105 Equation Transcription: Text Transcription: 6-m rho=1000 kg/m^3

Problem 107P A pressure cooker cooks a lot faster than an ordinary pan by maintaining a higher pressure and temperature inside. The lid of a pressure cooker is well sealed, and steam can escape only through an opening in the middle of the lid. A separate metal piece, the petcock, sits on top of this opening and prevents steam from escaping until the pressure force overcomes the weight of the petcock. The periodic escape of the steam in this manner prevents any potentially dangerous pressure buildup and keeps the pressure inside at a constant value, Determine the mass of the petcock of a pressure cooker whose operation pressure is 100 kPa gage and has an opening cross-sectional area of 4 mm2. Assume an atmospheric pressure of 101 kPa, and draw the free-body diagram of the petcock.

Problem 106P A vertical, frictionless piston-cylinder device contains a gas at 180 kPa absolute pressure. The atmospheric pressure outside is 100 kPa, and the piston area is 25 cm2. Determine the mass of the piston.

A glass tube is attached to a water pipe, as shown in Fig. P1-108. If the water pressure at the bottom of the tube is \(110 \mathrm{kPa}\) and the local atmospheric pressure is \(99 \mathrm{kPa}\), determine how high the water will rise in the tube, in \(\mathrm{m}\). Take the density of water to be \(1000 \mathrm{~kg} / \mathrm{m}^{3}\). FIGURE P1–108 Equation Transcription: Text Transcription: 110 kPa 99 kPa 1000 kg/m^3

Consider a U-tube whose arms are open to the atmosphere. Now equal volumes of water and light oil \((\rho= 49.3 \mathrm{lbm} / \mathrm{ft}^{3}\)) are poured from different arms. A person blows from the oil side of the U-tube until the contact surface of the two fluids moves to the bottom of the U-tube, and thus the liquid levels in the two arms are the same. If the fluid height in each arm is 30 in, determine the gage pressure the person exerts on the oil by blowing. FIGURE P1–109E Equation Transcription: Text Transcription: rho=49.3 lbm/ft^3 30 in

The basic barometer can be used as an altitude measuring device in airplanes. The ground control reports a barometric reading of \(753 \mathrm{mmHg}\) while the pilot's reading is \(690 \mathrm{mmHg}\). Estimate the altitude of the plane from ground level if the average air density is \(1.20 \mathrm{~kg} / \mathrm{m}^{3}\). Equation Transcription: Text Transcription: 753 mmHg 690 mmHg 1.20 kg/m^3 .

Repeat Prob. 1–112 for a pressure gage reading of \(180 \mathrm{kPa}\). Equation Transcription: Text Transcription: 180 kPa

A gasoline line is connected to a pressure gage through a double-U manometer, as shown in Fig. P1–112 on the next page. If the reading of the pressure gage is \(370 \mathrm{kPa}\), determine the gage pressure of the gasoline line. FIGURE P1–112 Equation Transcription: Text Transcription: 370 kPa

A water pipe is connected to a double-U manometer as shown in Fig. P1–111E at a location where the local atmospheric pressure is \(14.2 \mathrm{psia}\). Determine the absolute pressure at the center of the pipe. FIGURE P1–111E Equation Transcription: Text Transcription: 14.2 psia

Problem 114P The average atmospheric pressure on earth is approximated as a function of altitude by the relation Patm = 101.325 (1–0.02256z)5.256, where Patm is the atmospheric pressure in kPa and z is the altitude in km with z= 0 at sea level. Determine the approximate atmospheric pressures at Atlanta (z= 306 m), Denver (z= 1610 m), Mexico City (z= 2309 m), and the top of Mount Everest (z = 8848 m).

Problem 116P The variation of pressure with density in a thick gas layer is given by P= C?n, where C and n are constants. Noting that the pressure change across a differential fluid layer of thickness dz in the vertical z-direction is given as dP= ? ?g dz, obtain a relation for pressure as a function of elevation z. Take the pressure and density at z= 0 to be P0 and ?0, respectively.

Problem 117P Consider the flow of air through a wind turbine whose blades sweep an area of diameter D (in m). The average air velocity through the swept area is V (in m/s). On the bases of the units of the quantities involved, show that the mass flow rate of air (in kg/s) through the swept area is. proportional to air density, the wind velocity, and the square of the diameter of the swept area.

Problem 115P It is well-known that the temperature of the atmosphere varies with altitude. In the troposphere, which extends to an altitude of 11 km, for example, the variation of temperature can be approximated by T=T0 ??z, where T0 is the temperature at sea level, which can be taken to be 288.1.5 K, and ? = 0.0065 K/m. The gravitational acceleration also changes with altitude as g(z) =g0/(l + z/6,370,320)2 where g0 = 9.807 m/s2 and z is the elevation from sea level in m. Obtain a relation for the variation of pressure in the troposphere (a) by ignoring and (b) by considering the variation of g with altitude.

The drag force exerted on a car by air depends on a dimensionless drag coefficient, the density of air, the car velocity, and the frontal area of the car. That is, \(F_{D}=\) function \(\left(C_{\text {Drag }} A_{\text {front }}, \rho, V\right)\). Based on unit considerations alone, obtain a relation for the drag force. Equation Transcription: Text Transcription: F=function(C_Drag A_front, rho, V)

Problem 120P Consider a fish swimming 5 m below the free surface of water. The increase in the pressure exerted on the fish when it dives to a depth of 25 m below the free surface is (a) 196 Pa ________________ (b) 5400 Pa ________________ (c) 30,000 Pa ________________ (d) 196,000 Pa ________________ (e) 294,000 Pa

Problem 123P During a heating process, the temperature of an object rises by 10°C. This temperature rise is equivalent to a temperature rise of (a) l0°F ________________ (b)42°F ________________ (c) 18 K ________________ (d) 18 R ________________ (e) 283 K

Problem 122P Consider a 2-m deep swimming pool. The pressure difference between the top and bottom of the pool is (a)12.0 kPa ________________ (b) 19.6 kPa ________________ (c) 38.1 kPa ________________ (d)50.8 kPa ________________ (e)200 kPa

Problem 119P An apple loses 4.5 kJ of heat as it cools per °C drop in its temperature. The amount of heat loss from the apple per °F drop in its temperature is (a) 1.25 kJ ________________ (b)2.50 kJ ________________ (c) 5.0 kJ ________________ (d)8.1 kJ ________________ (e)4.1 kJ

A pressure cooker cooks a lot faster than an ordinary pan by maintaining a higher pressure and temperature inside. The lid of a pressure cooker is well sealed, and steam can escape only through an opening in the middle of the lid. A separate metal piece, the petcock, sits on top of this opening and prevents steam from escaping until the pressure force overcomes the weight of the petcock. The periodic escape of the steam in this manner prevents any potentially dangerous pressure buildup and keeps the pressure inside at a constant value. Determine the mass of the petcock of a pressure cooker whose operation pressure is \(100 \mathrm{kPa}\) gage and has an opening cross-sectional area of \(4 \mathrm{~mm}^{2}\). Assume an atmospheric pressure of \(101 \mathrm{kPa}\), and draw the free-body diagram of the petcock. Equation Transcription: Text Transcription: 100 kPa 4 mm^2 101 kPa

The constant-pressure specific heat of air at is . Express this value in , , , and .

A rock is thrown upward with a force of at a location where the local gravitational acceleration is . Determine the acceleration of the rock, in .

One of the most amusing things a person can experience is when a car in neutral appears to go uphill when its brakes are released. Can this really happen or is it an optical illusion? How can you verify if a road is pitched uphill or downhill?

A 4-kW resistance heater in a water heater runs for 3 hours to raise the water temperature to the desired level. Determine the amount of electric energy used in both kWh and kJ.

A astronaut took his bathroom scale (a spring scale and a beam scale (compares masses) to the moon where the local gravity is , Determine how much he will weigh (a) on the spring scale and (b) on the beam scale.

The gas tank of a car is filled with a nozzle that discharges gasoline at a constant flow rate. Based on unit considerations of quantities,obtain a relation for the filling time in terms of the volume V of the tank (in L) and the discharge rate of gasoline V (in L/s).

A pool of volume V (in ) is to be filled with water using a hose a diameter D (in m). If the average discharge velocity is V (in m/s) and the filling time is t (in s), obtain a relation for the volume of the pool based on considerations of quantities involved.

A large fraction of the thermal energy generated in the engine of a car is rejected to the air by the radiator through the circulating water. Should the radiator be analyzed as a closed system or as an open system? Explain.

You are trying to understand how a reciprocating air compressor (a piston-cylinder device) works. What system would you use? What type of system is this?

The basic barometer can be used as an altitude measuring device in airplanes. The ground control reports a barometric reading of while the pilot’s reading is . Estimate the altitude of the plane from ground level if the average air density is .

A water pipe is connected to a double-U manometer as shown in Fig. P1–111E at a location where the local atmospheric pressure is . Determine the absolute pressure at the center of the pipe.

A gasoline line is connected to a pressure gage through a double-U manometer, as shown in Fig. P1–112 on the next page. If the reading of the pressure gage is , determine the gage pressure of the gasoline line.

Repeat Prob. 1–112 for a pressure gage reading of .

The average atmospheric pressure on earth is approximated as a function of altitude by the relation , where is the atmospheric pressure in and is the altitude in km with at sea level. Determine the approximate atmospheric pressures at Atlanta , Denver , Mexico City , and the top of Mount Everest .

It is well-known that the temperature of the atmosphere varies with altitude. In the troposphere, which extends to an altitude of 11 km, for example, the variation of temperature can be approximated by , where is the temperature at sea level, which can be taken to be , and . The gravitational acceleration also changes with altitude as where and z is the elevation from sea level in m. Obtain a relation for the variation of pressure in the troposphere (a) by ignoring and (b) by considering the variation of g with altitude.

The variation of pressure with density in a thick gas layer is given by , where C and n are constants. Noting that the pressure change across a differential fluid layer of thickness dz in the vertical z-direction is given as , obtain a relation for pressure as a function of elevation z. Take the pressure and density at to be and , respectively.

Consider the flow of air through a wind turbine whose blades sweep an area of diameter D (in m). The average air velocity through the swept area is V (in m/s). On the bases of the units of the quantities involved, show that the mass flow rate of air (in ) through the swept area is proportional to air density, the wind velocity, and the square of the diameter of the swept area.

The drag force exerted on a car by air depends on a dimensionless drag coefficient, the density of air, the car velocity, and the frontal area of the car. That is, . Based on unit considerations alone, obtain a relation for the drag force

You are trying to understand how a reciprocating air compressor (a piston-cylinder device) works. What system would you use? What type of system is this?

A can of soft drink at room temperature is put into the refrigerator so that it will cool. Would you model the can of soft drink as a closed system or as an open system? Explain

What is the difference between intensive and extensive properties?

Is the weight of a system an extensive or intensive property?

Is the state of the air in an isolated room completely specified by the temperature and the pressure? Explain.

The molar specific volume of a system v is defined as the ratio of the volume of the system to the number of moles of substance contained in the system. Is this an extensive or intensive property?

What is a quasi-equilibrium process? What is its importance in engineering?

Define the isothermal, isobaric, and isochoric processes.

How would you describe the state of the water in a bathtub? How would you describe the process that this water experiences as it cools?

When analyzing the acceleration of gases as they flow through a nozzle, what would you choose as your system? What type of system is this?

What is specific gravity? How is it related to density?

The density of atmospheric air varies with elevation, decreasing with increasing altitude. (a) Using the data given in the table, obtain a relation for the variation of density with elevation, and calculate the density at an elevation of 7000 m. (b) Calculate the mass of the atmosphere using the correlation you obtained. Assume the earth to be a perfect sphere with a radius of 6377 km, and take the thickness of the atmosphere to be 25 km.

What are the ordinary and absolute temperature scales in the SI and the English system?

Consider an alcohol and a mercury thermometer that read exactly 0C at the ice point and 100C at the steam point. The distance between the two points is divided into 100 equal parts in both thermometers. Do you think these thermometers will give exactly the same reading at a temperature of, say, 60C? Explain.

Consider two closed systems A and B. System A contains 3000 kJ of thermal energy at 20C, whereas system B contains 200 kJ of thermal energy at 50C. Now the systems are brought into contact with each other. Determine the direction of any heat transfer between the two systems.

The deep body temperature of a healthy person is 37C. What is it in kelvins?

What is the temperature of the heated air at 150C in F and R?

The temperature of a system rises by 70C during a heating process. Express this rise in temperature in kelvins.

The flash point of an engine oil is 363F. What is the absolute flash-point temperature in K and R?

The temperature of ambient air in a certain location is measured to be 240C. Express this temperature in Fahrenheit (F), Kelvin (K), and Rankine (R) units.

The temperature of a system drops by 45F during a cooling process. Express this drop in temperature in K, R, and C.

Explain why some people experience nose bleeding and some others experience shortness of breath at high elevations.

A health magazine reported that physicians measured 100 adults blood pressure using two different arm positions: parallel to the body (along the side) and perpendicular to the body (straight out). Readings in the parallel position were up to 10 percent higher than those in the perpendicular position, regardless of whether the patient was standing, sitting, or lying down. Explain the possible cause for the difference.

Someone claims that the absolute pressure in a liquid of constant density doubles when the depth is doubled. Do you agree? Explain.

Express Pascals law, and give a real-world example of it.

Consider two identical fans, one at sea level and the other on top of a high mountain, running at identical speeds. How would you compare (a) the volume flow rates and (b) the mass flow rates of these two fans?

A vacuum gage connected to a chamber reads 35 kPa at a location where the atmospheric pressure is 92 kPa. Determine the absolute pressure in the chamber.

The pressure in a compressed air storage tank is 1200 kPa. What is the tanks pressure in (a) kN and m units; (b) kg, m, and s units; and (c) kg, km, and s units?

The pressure in a water line is 1500 kPa. What is the line pressure in (a) lb/ft2 units and (b) lbf/in2 (psi) units?

If the pressure inside a rubber balloon is 1500 mmHg, what is this pressure in pounds-force per square inch (psi)?

A manometer is used to measure the air pressure in a tank. The fluid used has a specific gravity of 1.25, and the differential height between the two arms of the manometer is 28 in. If the local atmospheric pressure is 12.7 psia, determine the absolute pressure in the tank for the cases of the manometer arm with the (a) higher and (b) lower fluid level being attached to the tank.

The water in a tank is pressurized by air, and the pressure is measured by a multifluid manometer as shown in Fig. P150. Determine the gage pressure of air in the tank if h1 5 0.2 m, h2 5 0.3 m, and h3 5 0.4 m. Take the densities of water, oil, and mercury to be 1000 kg/m3 , 850 kg/m3 , and 13,600 kg/m3 , respectively.

Determine the atmospheric pressure at a location where the barometric reading is 750 mmHg. Take the density of mercury to be 13,600 kg/m3 .

A 200-pound man has a total foot imprint area of 72 in2 . Determine the pressure this man exerts on the ground if (a) he stands on both feet and (b) he stands on one foot.

The gage pressure in a liquid at a depth of 3 m is read to be 42 kPa. Determine the gage pressure in the same liquid at a depth of 9 m.

The absolute pressure in water at a depth of 9 m is read to be 185 kPa. Determine (a) the local atmospheric pressure, and (b) the absolute pressure at a depth of 5 m in a liquid whose specific gravity is 0.85 at the same location.

Determine the pressure exerted on the surface of a submarine cruising 175 ft below the free surface of the sea. Assume that the barometric pressure is 14.7 psia and the specific gravity of seawater is 1.03.

Consider a 70-kg woman who has a total foot imprint area of 400 cm2 . She wishes to walk on the snow, but the snow cannot withstand pressures greater than 0.5 kPa. Determine the minimum size of the snowshoes needed (imprint area per shoe) to enable her to walk on the snow without sinking.

The vacuum pressure of a condenser is given to be 80 kPa. If the atmospheric pressure is 98 kPa, what is the gage pressure and absolute pressure in kPa, kN/m2 , lbf/in2 , psi, and mmHg.

The barometer of a mountain hiker reads 750 mbars at the beginning of a hiking trip and 650 mbars at the end. Neglecting the effect of altitude on local gravitational acceleration, determine the vertical distance climbed. Assume an average air density of 1.20 kg/m3 .

The basic barometer can be used to measure the height of a building. If the barometric readings at the top and at the bottom of a building are 675 and 695 mmHg, respectively, determine the height of the building. Take the densities of air and mercury to be 1.18 kg/m3 and 13,600 kg/m3 , respectively.

Solve Prob. 159 using EES (or other) software. Print out the entire solution, including the numerical results with proper units.

The hydraulic lift in a car repair shop has an output diameter of 30 cm and is to lift cars up to 2000 kg. Determine the fluid gage pressure that must be maintained in the reservoir.

A gas is contained in a vertical, frictionless piston cylinder device. The piston has a mass of 3.2 kg and a crosssectional area of 35 cm2 . A compressed spring above the piston exerts a force of 150 N on the piston. If the atmospheric pressure is 95 kPa, determine the pressure inside the cylinder.

Reconsider Prob. 162. Using EES (or other) software, investigate the effect of the spring force in the range of 0 to 500 N on the pressure inside the cylinder. Plot the pressure against the spring force, and discuss the results.

Both a gage and a manometer are attached to a gas tank to measure its pressure. If the reading on the pressure gage is 80 kPa, determine the distance between the two fluid levels of the manometer if the fluid is (a) mercury (r 5 13,600 kg/m3 ) or (b) water (r 5 1000 kg/m3 ).

Reconsider Prob. 164. Using EES (or other) software, investigate the effect of the manometer fluid density in the range of 800 to 13,000 kg/m3 on the differential fluid height of the manometer. Plot the differential fluid height against the density, and discuss the results.

A manometer containing oil (r 5 850 kg/m3 ) is attached to a tank filled with air. If the oil-level difference between the two columns is 80 cm and the atmospheric pressure is 98 kPa, determine the absolute pressure of the air in the tank.

A mercury manometer (r 5 13,600 kg/m3 ) is connected to an air duct to measure the pressure inside. The difference in the manometer levels is 15 mm, and the atmospheric pressure is 100 kPa. (a) Judging from Fig. P167, determine if the pressure in the duct is above or below the atmospheric pressure. (b) Determine the absolute pressure in the duct.

Repeat Prob. 167 for a differential mercury height of 45 mm.

The pressure in a natural gas pipeline is measured by the manometer shown in Fig. P169E 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.

Repeat Prob. 169E by replacing air by oil with a specific gravity of 0.69.

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.

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 person, determine how high the blood will rise in the tube. Take the density of the blood to be 1050 kg/m3 .

Determine the pressure exerted on a diver at 45 m below the free surface of the sea. Assume a barometric pressure of 101 kPa and a specific gravity of 1.03 for seawater.

Consider a U-tube whose arms are open to the atmosphere. Now water is poured into the U-tube from one arm, and light oil (r 5 790 kg/m3 ) from the other. One arm contains 70-cm-high water, while the other arm contains both fluids with an oil-to-water height ratio of 4. Determine the height of each fluid in that arm.

Consider a double-fluid manometer attached to an air pipe shown in Fig. P175. If the specific gravity of one fluid is 13.55, determine the specific gravity of the other fluid for the indicated absolute pressure of air. Take the atmospheric pressure to be 100 kPa.

Freshwater and seawater flowing in parallel horizontal pipelines are connected to each other by a double U-tube manometer, as shown in Fig. P176. Determine the pressure difference between the two pipelines. Take the density of seawater at that location to be r 5 1035 kg/m3 . Can the air column be ignored in the analysis?

Repeat Prob. 176 by replacing the air with oil whose specific gravity is 0.72.

Calculate the absolute pressure, P1, of the manometer shown in Fig. P178 in kPa. The local atmospheric pressure is 758 mmHg.

Consider the manometer in Fig. P178. If the specific weight of fluid A is 100 kN/m3 , what is the absolute pressure, in kPa, indicated by the manometer when the local atmospheric pressure is 90 kPa?

Consider the manometer in Fig. P178. If the specific weight of fluid B is 20 kN/m3 , what is the absolute pressure, in kPa, indicated by the manometer when the local atmospheric pressure is 720 mmHg?

Consider the system shown in Fig. P181. If a change of 0.7 kPa in the pressure of air causes the brinemercury interface in the right column to drop by 5 mm in the brine level in the right column while the pressure in the brine pipe remains constant, determine the ratio of A2/A1.

What is the value of the engineering software packages in (a) engineering education and (b) engineering practice?

Determine a positive real root of this equation using EES: 2x3 2 10x0.5 2 3x 5 23

Solve this system of two equations with two unknowns using EES: x3 2 y2 5 7.75 3xy 1 y 5 3.5

Solve this system of three equations with three unknowns using EES: x2 y 2 z 5 1 x 2 3y0.5 1 xz 5 22 x 1 y 2 z 5 2

Solve this system of three equations with three unknowns using EES: 2x 2 y 1 z 5 7 3x2 1 3y 5 z 1 3 xy 1 2z 5 4

Specific heat is defined as the amount of energy needed to increase the temperature of a unit mass of a substance by one degree. The specific heat of water at room temperature is 4.18 kJ/kgC in SI unit system. Using the unit conversion function capability of EES, express the specific heat of water in (a) kJ/kgK, (b) Btu/lbmF, (c) Btu/lbmR, and (d ) kcal/kgC units.

The weight of bodies may change somewhat from one location to another as a result of the variation of the gravitational acceleration g with elevation. Accounting for this variation using the relation in Prob. 18, determine the weight of an 80-kg person at sea level (z 5 0), in Denver (z 5 1610 m), and on the top of Mount Everest (z 5 8848 m).

A man goes to a traditional market to buy a steak for dinner. He finds a 12-oz steak (1 lbm 5 16 oz) for $5.50. He then goes to the adjacent international market and finds a 300-g steak of identical quality for $5.20. Which steak is the better buy?

What is the weight of a 1-kg substance in N, kN, kgm/s2 , kgf, lbmft/s2 , and lbf?

A hydraulic lift is to be used to lift a 2500 kg weight by putting a weight of 25 kg on a piston with a diameter of 10 cm. Determine the diameter of the piston on which the weight is to be placed.

The efficiency of a refrigerator increases by 3 percent for each C rise in the minimum temperature in the device. What is the increase in the efficiency for each (a) K, (b) F, and (c) R rise in temperature?

Hyperthermia of 5C (i.e., 5C rise above the normal body temperature) is considered fatal. Express this fatal level of hyperthermia in (a) K, (b) F, and (c) R.

A house is losing heat at a rate of 1800 kJ/h per C temperature difference between the indoor and the outdoor temperatures. Express the rate of heat loss from this house per (a) K, (b) F, and (c) R difference between the indoor and the outdoor temperature.

The average temperature of the atmosphere in the world is approximated as a function of altitude by the relation Tatm 5 288.15 2 6.5z where Tatm is the temperature of the atmosphere in K and z is the altitude in km with z 5 0 at sea level. Determine the average temperature of the atmosphere outside an airplane that is cruising at an altitude of 12,000 m.

Joe Smith, an old-fashioned engineering student, believes that the boiling point of water is best suited for use as the reference point on temperature scales. Unhappy that the boiling point corresponds to some odd number in the current absolute temperature scales, he has proposed a new absolute temperature scale that he calls the Smith scale. The temperature unit on this scale is smith, denoted by S, and the boiling point of water on this scale is assigned to be 1000 S. From a thermodynamic point of view, discuss if it is an acceptable temperature scale. Also, determine the ice point of water on the Smith scale and obtain a relation between the Smith and Celsius scales.

It is well-known that cold air feels much colder in windy weather than what the thermometer reading indicates because of the chilling effect of the wind. This effect is due to the increase in the convection heat transfer coefficient with increasing air velocities. The equivalent wind chill temperature in F is given by [ASHRAE, Handbook of Fundamentals (Atlanta, GA, 1993), p. 8.15] Tequiv 5 91.4 2 (91.4 2 Tambient) 3 (0.475 2 0.0203V 1 0.304!V) where V is the wind velocity in mi/h and Tambient is the ambient air temperature in F in calm air, which is taken to be air with light winds at speeds up to 4 mi/h. The constant 91.4F in the given equation is the mean skin temperature of a resting person in a comfortable environment. Windy air at temperature Tambient and velocity V will feel as cold as the calm air at temperature Tequiv. Using proper conversion factors, obtain an equivalent relation in SI units where V is the wind velocity in km/h and Tambient is the ambient air temperature in C.

Reconsider Prob. 197E. Using EES (or other) software, plot the equivalent wind chill temperatures in F as a function of wind velocity in the range of 4 to 40 mph for the ambient temperatures of 20, 40, and 60F. Discuss the results.

A vertical pistoncylinder device contains a gas at a pressure of 100 kPa. The piston has a mass of 5 kg and a diameter of 12 cm. Pressure of the gas is to be increased by placing some weights on the piston. Determine the local atmospheric pressure and the mass of the weights that will double the pressure of the gas inside the cylinder.

An air-conditioning system requires a 35-m-long section of 15-cm diameter duct work to be laid underwater. Determine the upward force the water will exert on the duct. Take the densities of air and water to be 1.3 kg/m3 and 1000 kg/m3 , respectively.

The average body temperature of a person rises by about 2C during strenuous exercise. What is the rise in the body temperature in (a) K, (b) F, and (c) R during strenuous exercise?

Balloons are often filled with helium gas because it weighs only about one-seventh of what air weighs under identical conditions. The buoyancy force, which can be expressed as Fb 5 rairgVballoon, will push the balloon upward. If the balloon has a diameter of 12 m and carries two people, 85 kg each, deter mine the acceleration of the balloon when it is first released. Assume the density of air is r 5 1.16 kg/m3 , and neglect the weight of the ropes and the cage.

Reconsider Prob. 1102. Using EES (or other) software, investigate the effect of the number of people carried in the balloon on acceleration. Plot the acceleration against the number of people, and discuss the results.

Determine the maximum amount of load, in kg, the balloon described in Prob. 1102 can carry.

The lower half of a 6-m-high cylindrical container is filled with water (r 5 1000 kg/m3 ) and the upper half with oil that has a specific gravity of 0.85. Determine the pressure difference between the top and bottom of the cylinder.

A vertical, frictionless pistoncylinder device contains a gas at 180 kPa absolute pressure. The atmospheric pressure outside is 100 kPa, and the piston area is 25 cm2 . Determine the mass of the piston.

A pressure cooker cooks a lot faster than an ordinary pan by maintaining a higher pressure and temperature inside. The lid of a pressure cooker is well sealed, and steam can escape only through an opening in the middle of the lid. A separate metal piece, the petcock, sits on top of this opening and prevents steam from escaping until the pressure force overcomes the weight of the petcock. The periodic escape of the steam in this manner prevents any potentially dangerous pressure buildup and keeps the pressure inside at a constant value. Determine the mass of the petcock of a pressure cooker whose operation pressure is 100 kPa gage and has an opening cross-sectional area of 4 mm2 . Assume an atmospheric pressure of 101 kPa, and draw the free-body diagram of the petcock.

A glass tube is attached to a water pipe, as shown in Fig. P1108. If the water pressure at the bottom of the tube is 110 kPa and the local atmospheric pressure is 99 kPa, determine how high the water will rise in the tube, in m. Take the density of water to be 1000 kg/m3 .

Consider a U-tube whose arms are open to the atmosphere. Now equal volumes of water and light oil (r 5 49.3 lbm/ft3 ) are poured from different arms. A person blows from the oil side of the U-tube until the contact surface of the two fluids moves to the bottom of the U-tube, and thus the liquid levels in the two arms are the same. If the fluid height in each arm is 30 in, determine the gage pressure the person exerts on the oil by blowing.

The basic barometer can be used as an altitudemeasuring device in airplanes. The ground control reports a barometric reading of 753 mmHg while the pilots reading is 690 mmHg. Estimate the altitude of the plane from ground level if the average air density is 1.20 kg/m3 .

A water pipe is connected to a double-U manometer as shown in Fig. P1111E at a location where the local atmospheric pressure is 14.2 psia. Determine the absolute pressure at the center of the pipe.

A gasoline line is connected to a pressure gage through a double-U manometer, as shown in Fig. P1112 on the next page. If the reading of the pressure gage is 370 kPa, determine the gage pressure of the gasoline line.

Repeat Prob. 1112 for a pressure gage reading of 180 kPa.

The average atmospheric pressure on earth is approximated as a function of altitude by the relation Patm 5 101.325 (1 2 0.02256z) 5.256, where Patm is the atmospheric pressure in kPa and z is the altitude in km with z 5 0 at sea level. Determine the approximate atmospheric pressures at Atlanta (z 5 306 m), Denver (z 5 1610 m), Mexico City (z 5 2309 m), and the top of Mount Everest (z 5 8848 m).

It is well-known that the temperature of the atmosphere varies with altitude. In the troposphere, which extends to an altitude of 11 km, for example, the variation of temperature can be approximated by T 5 T0 2 bz , where T0 is the temperature at sea level, which can be taken to be 288.15 K, and b 5 0.0065 K/m. The gravitational acceleration also changes with altitude as g(z) 5 g0/(1 1 z/6,370,320)2 where g0 5 9.807 m/s2 and z is the elevation from sea level in m. Obtain a relation for the variation of pressure in the troposphere (a) by ig

The variation of pressure with density in a thick gas layer is given by P 5 Crn , where C and n are constants. Noting that the pressure change across a differential fluid layer of thickness dz in the vertical z-direction is given as dP 5 2 rg dz , obtain a relation for pressure as a function of elevation z. Take the pressure and density at z 5 0 to be P0 and r0, respectively.

Consider the flow of air through a wind turbine whose blades sweep an area of diameter D (in m). The average air velocity through the swept area is V (in m/s). On the bases of the units of the quantities involved, show that the mass flow rate of air (in kg/s) through the swept area is proportional to air density, the wind velocity, and the square of the diameter of the swept area.

The drag force exerted on a car by air depends on a dimensionless drag coefficient, the density of air, the car velocity, and the frontal area of the car. That is, FD 5 function (CDrag Afront, r, V). Based on unit considerations alone, obtain a relation for the drag force.

An apple loses 4.5 kJ of heat as it cools per C drop in its temperature. The amount of heat loss from the apple per F drop in its temperature is (a) 1.25 kJ (b) 2.50 kJ (c) 5.0 kJ (d ) 8.1 kJ (e) 4.1 kJ

Consider a fish swimming 5 m below the free surface of water. The increase in the pressure exerted on the fish when it dives to a depth of 25 m below the free surface is (a) 196 Pa (b) 5400 Pa (c) 30,000 Pa (d ) 196,000 Pa (e) 294,000 Pa

The atmospheric pressures at the top and the bottom of a building are read by a barometer to be 96.0 and 98.0 kPa. If the density of air is 1.0 kg/m3 , the height of the building is (a) 17 m (b) 20 m (c) 170 m (d ) 204 m (e) 252 m

Consider a 2-m deep swimming pool. The pressure difference between the top and bottom of the pool is (a) 12.0 kPa (b) 19.6 kPa (c) 38.1 kPa (d ) 50.8 kPa (e) 200 kPa

During a heating process, the temperature of an object rises by 10C. This temperature rise is equivalent to a temperature rise of (a) 10F (b) 42F (c) 18 K (d ) 18 R (e) 283 K

At sea level, the weight of 1 kg mass in SI units is 9.81 N. The weight of 1 lbm mass in English units is (a) 1 lbf (b) 9.81 lbf (c) 32.2 lbf (d ) 0.1 lbf (e) 0.031 lbf

Write an essay on different temperature measurement devices. Explain the operational principle of each device, its advantages and disadvantages, its cost, and its range of applicability. Which device would you recommend for use in the following cases: taking the temperatures of patients in a doctors office, monitoring the variations of temperature of a car engine block at several locations, and monitoring the temperatures in the furnace of a power plant?

Write an essay on the various mass- and volumemeasurement devices used throughout history. Also, explain the development of the modern units for mass and volume.