ch02_eu

# ch02_eu - ENGLISH UNIT PROBLEMS SOLUTION MANUAL CHAPTER 2...

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ENGLISH UNIT PROBLEMS SOLUTION MANUAL CHAPTER 2

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Borgnakke and Sonntag CHAPTER 2 SUBSECTION PROB NO. Concept-Study Guide Problems 90-95 Properties and Units 96 Force, Energy and Specific Volume 97-102 Pressure, Manometers and Barometers 103-111 Temperature 112-113
Borgnakke and Sonntag Concept Problems

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Borgnakke and Sonntag 2.90 E A mass of 2 lbm has acceleration of 5 ft/s 2 , what is the needed force in lbf? Solution: Newtons 2 nd law: F = ma F = ma = 2 lbm × 5 ft/s 2 = 10 lbm ft/s 2 = 10 32.174 lbf = 0.31 lbf
Borgnakke and Sonntag 2.91 E How much mass is in 0.25 gallon of liquid mercury (Hg)? Atmospheric air? Solution: A volume of 1 gal equals 231 in 3 , see Table A.1. From Figure 2.7 the density is in the range of 10 000 kg/m 3 = 624.28 lbm/ft 3 , so we get m = ρ V = 624.3 lbm/ft 3 × 0.25 × (231/12 3 ) ft 3 = 20.86 lbm A more accurate value from Table F.3 is ρ = 848 lbm/ft 3 . For the air we see in Figure 2.7 that density is about 1 kg/m 3 = 0.06243 lbm/ft 3 so we get m = ρ V = 0.06243 lbm/ft 3 × 0.25 × (231/12 3 ) ft 3 = 0.00209 lbm A more accurate value from Table F.4 is ρ = 0.073 lbm/ft 3 at 77 F, 1 atm.

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Borgnakke and Sonntag 2.92 E Can you easily carry a one gallon bar of solid gold? Solution: The density of solid gold is about 1205 lbm/ft 3 from Table F.2, we could also have read Figure 2.7 and converted the units. V = 1 gal = 231 in 3 = 231 × 12 -3 ft 3 = 0.13368 ft 3 Therefore the mass in one gallon is m = ρ V = 1205 lbm/ft 3 × 0.13368 ft 3 = 161 lbm and some people can just about carry that in the standard gravitational field.
Borgnakke and Sonntag 2.93 E What is the temperature of –5F in degrees Rankine? Solution: The offset from Fahrenheit to Rankine is 459.67 R, so we get T R = T F + 459.67 = -5 + 459.67 = 454.7 R 2.94 E What is the smallest temperature in degrees Fahrenheit you can have? Rankine? Solution: The lowest temperature is absolute zero which is at zero degrees Rankine at which point the temperature in Fahrenheit is negative T R = 0 R = 459.67 F 2.95 E What is the relative magnitude of degree Rankine to degree Kelvin Look in Table A.1 p. 757: 1 K = 1 o C = 1.8 R = 1.8 F 1 R = 5

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Borgnakke and Sonntag Properties and Units
Borgnakke and Sonntag 2.96 E An apple weighs 0.2 lbm and has a volume of 6 in 3 in a refrigerator at 38 F. What is the apple density? List three intensive and two extensive properties for the apple. Solution: ρ = m V = 0.2 6 lbm in 3 = 0.0333 lbm in 3 = 57.6 lbm ft 3 Intensive ρ = 57.6 lbm ft 3 ; v = 1 ρ = 0.0174 ft 3 lbm T = 38 F; P = 14.696 lbf/in 2 Extensive m = 0.2 lbm V = 6 in 3 = 0.026 gal = 0.00347 ft 3

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Borgnakke and Sonntag 2.97 E A steel piston of 5 lbm is in the standard gravitational field where a force of 10 lbf
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ch02_eu - ENGLISH UNIT PROBLEMS SOLUTION MANUAL CHAPTER 2...

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