Modern Engineering Thermodynamics

Problems 723
a. If the monster consumed its charged energy at a rate of
1.30 MJ/h, how long before it needed to be recharged again?
b. If the monster had a mass of 100. kg, what would be its
mean metabolic rate in MJ/d if it were a normal mammal?
14.* The heat of formation of glucose ðC 6 H 12 O 6 Þ is –996.4 MJ/
kgmole. Using the material presented in Chapter 15, determine
a. The amount of heat liberated (i.e., the heat of reaction) at
the standard reference state as 1 mole of glucose is
metabolized according to the reaction
C 6 H 12 O 6 + 6O ð 2
Þ ! 6H 2 OðlÞ
ð Þ+ 6CO ð 2 Þ+ heat
b. How long does it take to completely metabolize 1.00 kg of
pure glucose at a basal metabolic rate of 0.300 MJ/h?
15.* Human blood contains 1.00 gram of glucose ðC 6 H 12 O 6 Þ per
liter, and the average person contains 5.20 L of blood. In
metabolizing glucose, 17.1 MJ/kg of energy is released, of which
50.0% is lost as heat and 50.0% is used to make adenosine
triphosphate (ATP).
a. How much energy could be stored in the ATP of the blood
of an average person?
b. If the metabolic heat of the glucose is removed from the
body by the evaporation of perspiration, how much
perspiration is evaporated per gram of glucose metabolized?
Assume the heat of vaporization of perspiration ðH 2 OÞ is
40.6 MJ/kgmole.
16.* During a weekend of fun and frolic, Homer, a humanities
student, consumes 8.50 kg of beer with a metabolizable energy
content of 1.10 MJ/kg. Homer then went to bed with the intent
of sleeping off his entire caloric intake of beer. Assuming he
falls asleep at 2:00 AM Wednesday morning, when should he
wake up?
17.* In an experiment, the contribution of Joe’s brain to his total
BMR was found to be 5.00 × 10 –2 MJ/h.
a. What is Joe’s total mass?
b. How long would it take Joe to metabolize the energy content
of one candy bar containing 0.750 MJ while resting?
18.* A serious problem that arises in performing surgery on cats and
small dogs is the additional heat loss produced from an open
body cavity. For these small animals, this type of surgery
effectively doubles the normal heat loss rate. If the anesthetic
used depresses the BMR of a 5.00 kg dog by 50.0%, estimate the
resulting reduction in the animal’s body temperature from its
normal body temperature of 102°F (39.2°C) during 2.00 h of
a. Minor surgery not requiring the body cavity to be opened.
b. Major surgery requiring an open body cavity procedure.
Assume the body of the dog has a specific heat of
4.17 kJ/(kg · K).
19.* What is Superman’s top flying speed, if he gets all his energy by
eating as many 1.00 MJ chocolate candy bars as he wishes?
Neglect his potential energy, aerodynamic drag, and all other
losses.
20.* If you consume 25.0 Calories per day more food energy than
you use, how many years will it take you to gain 10.0 kg of fat
if there are 33.1 MJ per kg of body fat?
21.* During a basal metabolic test, Steve consumes 460. L of O 2 .
a. What is Steve’s body mass?
b. What is the change in his BMR oxygen intake if he loses
15.0 kg of body mass?
22.* Broiled lobster contains 3.60 MJ/kg of metabolizable food
energy. If Sharla has 45.0 min of hard cycling planned later in
the day, how much lobster can she eat so that she will be sure
not to gain weight?
23.* Suzanne Malaxos, 27, from Perth Australia, won the 12th
annual Empire State Building Run-Up in New York City by
climbing the 102 story building in 12 min and 24 s. If her body
mass is 50.0 kg, and each story is 4.00 m high, determine the
amount of body fat she consumed in the race. Assume a muscle
energy conversion efficiency of 25.0% and a body fat energy
content of 33.1 MJ/kg.
24.* You are at a tailgate party before a baseball game and have just
eaten three hot dogs with chili. The mass of the container and
the remaining contents of your quarter barrel of beer is 30.3 kg.
How many times would you have to lift this barrel 0.500 m in
2.00 s to work off the energy content of the hot dogs? How
many hours would it take to do this?
25. Gasoline has a heating value of 20.0 × 10 3 Btu/lbm. How many
10.0 oz colas must Ted drink to produce enough power by
turning a crank to light a 100. W lightbulb for the same number
of hours that an internal combustion engine running on
1.00 lbm of gasoline with an overall efficiency of 25.0% could
light the same bulb?
26.* Mark decides to build a cabin cruiser. After many hours of sawing
wood, it is determined that the sawing required a total of 63.0 MJ
of energy from Mark and 15.0% of this energy came from
protein (at 17.2 MJ/kg), 60.0% came from fat (at 33.1 MJ/kg),
and 25.0% came from carbohydrates (at 17.2 MJ/kg). Determine
the mass of protein, fat, and carbohydrates consumed in the
process.
27.* A 60.0 kg mountain climber makes a vertical climb of 2000. m
in 5.90 h. From a chemical analysis of the urine samples
collected during the climb, it is found that 2.00 × 10 –2 kg of
water-free protein is catabolized. Assuming a 25.0% muscle
energy conversion efficiency, find
a. The percentage of the total energy need for the climb that
came from protein and the percentage that came from fat.
b. The mass of natural (wet) fat catabolized (i.e., consumed)
during the climb.
28.* If you consume two hamburgers, one regular fries, and one
10 oz cola, how many hours on this meal alone can you
(a) cross country ski, (b) play tennis, or (c) watch television?
29.* Brian is somewhat overweight and calculates that his excess
body fat contains 18.0 miles of extra small blood vessels. Brian’s
weight is stable, but he consumes 10.5 MJ/d of metabolizable
food energy. To reduce his weight, he decides to eat one fewer
cheeseburger per day plus jog for one hour per day.
a. How much extra fat does Brian have at the beginning of
his diet?
b. How many days does it take for Brian to eliminate this fat?
30.* Steve is jogging at a constant speed of 5.00 mph and encounters a
hill that requires an average energy expenditure rate of 3.10 MJ/h.
If the hill is 0.400 mi long, determine the mass of natural state
foods that Steve must consume to replenish the energy spent
climbing the hill, if he consumes
a. Only carbohydrate with an energy content of 4.20 MJ/kg.
b. Only protein with an energy content of 8.40 MJ/kg.
c. Only fat with an energy content of 33.1 MJ/kg.
31.* In a laboratory experiment, two engineering students are asked
to determine the caloric value of a commercial brand of diet
cocoa. They are provided with a bomb calorimeter, which had
to be calibrated by measuring the heat liberated by a substance