While running, a 70 kg student generates thermal energy at a rate of 1400 W . To

Question

While running, a 70 kg student generates thermal energy at a rate of 1400 W . To maintain a constant body temperature of 39 C , this energy must be removed by perspiration or other mechanisms.

Part A If these mechanisms failed and the heat could not flow out of the student's body, for what amount of time could a student run before irreversible body damage occurred? (Protein structures in the body are damaged irreversibly if the body temperature rises to 44 C or above. The specific heat capacity of a typical human body is 3480 J/(kgK) , slightly less than that of water. The difference is due to the presence of protein, fat, and minerals, which have lower specific heats.)

Explanation / Answer

delta T = 44 - 39 = 5 0C

Q = m c delta T = 70 * 3480 * 5 = 1.218 * 106

Total emergy = 1.218 * 106

1400 * t = 1.218 * 106

t = 1.218 * 106 / 1400

t = 870 s = 14.5 min

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