Approximately 80% of the energy used by the body must be dissipated thermally. T

Question

Approximately 80% of the energy used by the body must be dissipated thermally. The mechanisms available to eliminate this energy are radiation, evaporation of sweat, evaporation from the lungs, conduction, and convection. In this question, we will focus on the evaporation of sweat alone, although all of these mechanisms are needed to survive. The latent heat of vaporization of sweat at body temperature (37C) is 2.42×106 J/kg and the specific heat of a body is approximately 3500 J/(kgC).

If the jogger produces 2400 kJ/h of excess thermal energy but cannot dissipate it in any way, how long before his temperature gets to the dangerously high 40C?

Explanation / Answer

heat = mass * specific heat * change in temperature

let the mass be m so

heat required = m * 3500 * (40 - 37)

heat required = m * 10500 J

time it'll take = m * 10500 / 2400000

time it'll take = 0.004375 * m hours

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