Question

Earlier this semester, we discussed how the concepts of work, energy, and power can be applied to understand the physical processes that govern biological systems. In this assignment, you will extend these ideas by examining the use of thermal energy and mechanical energy for biological systems. To complete this, you wil need to review Ch. 5, to read Ch. 12 on the laws of thermodynamics, and to use the table given below. This extra credit project will add 42 points to your overall quiz score. Energy consumption in watts Oxygen consumption in liters 02/min 83 0.24 0.34 0.36 0.60 0.80 1.14 1.21 126 1.36 1.56 1.96 2.00 2.12 2.28 Sitting at rest Standing relaxed Sitting in class Walking (5 km/h) Cycling (13-18 km/m) 120 210 280 400 Playing tennis 440 475 545 685 700 740 800 Ice skating (14.5 km/h) Climbing stairs (116/min) Cycling (21 km/h) Punning cross-country Playing basketball

Answer 1

(a) first we will convert Kcal to Joules

Note that in 1 Cal, we have 4.186 J

Therefore, Q = 400 kcal = 8.37e5 J

Therefore, mass of water evaporated,m = 8.37e5 / 2.5e6

m = 0.3348 kg

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(b) mass of fat burned = 400 kcal * 0.5 hr / 9 kcal = 22e-3 Kg

Therefore, fraction of water =  22e-3 Kg / 0.3348 kg

fraction of water = 0.06637

or 6.7 %