P2-3) It is important for the body to be able to cool itself even during moderate exercise. Suppose a 70kg man runs on a treadmill for 30min and at a (total) metabolic energy expenditure rate of 1000W. Part 1 (. Remembering that the human body has a 25% efficiency (“what you get”/”what you had to pay”; textbook sect. 11.2), estimate the amount of (mechanical) work done on the treadmill during that time. A) 1350 kJ B) 1800 kJ C) 1000 kJ D) 450 kJ
P2-3) It is important for the body to be able to cool itself even during
moderate exercise. Suppose a 70kg man runs on a treadmill for 30min and at a (total)
Part 1 (. Remembering that the human body has a 25% efficiency (“what you
get”/”what you had to pay”; textbook sect. 11.2), estimate the amount of (mechanical)
work done on the treadmill during that time.
A) 1350 kJ
B) 1800 kJ
C) 1000 kJ
D) 450 kJ
Part 2 ). Using the 1st law of
lost in heat during that time. (Hint: see textbook, Section 11.2, and also the lecture notes
#45, “Application of the 1st law of thermo to the human body” – CASE 1).
A) 1350 kJ
B) 1800 kJ
C) 1000 kJ
D) 450 kJ
Part 3 ). Suppose also that the man cannot perspire; and cannot lose any heat via
air-tight spacesuit but w/o portable cooling unit). By how much would the man’s body
temperature increase at the end of the 30min exercise? Express your answer in o
C.
A) 0.5
B) 1.4
C) 3.1
D) 5.7
E) 8.8
Part 4 ( Suppose the man is allowed to run without clothing, and in a room in
which the temperature of the air, walls, floor and ceiling are all equal to that of his skin
temperature. What is the net heat energy dissipated through radiative, conductive and
convective
A) 0 kJ
B) 450 kJ
C) 1350 kJ
D) 1800 kJ
Part 5 (. Finally, let us consider the man’s heat loss through perspiration while
exercising under the conditions stated in Parts 1 and 4. Calculate the amount of sweat
produced to allow evaporation cooling to maintain the skin and body near normal levels.
A) 0.56 kg
B) 1.12 kg
C) 3.80 kg
D) 5.60 kg
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